Charging Lithium batteries with stock alternator

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astrnmrtom
Posts: 167
Joined: Thu Oct 31, 2019 8:49 pm

Charging Lithium batteries with stock alternator

Post by astrnmrtom »

I'm considering upgrading from AGMs to lithium, and while my charger/converter is compatible, and so is my solar charger, it's the original alternator that concerns me. My ' 98 Serengeti has the original diode based battery charge splitter/isolator so the alternator will always see some load from the starter batteries. Is that enough to protect the alternator from overheating by charging the lithium at the same time, or do I need to add a DC to DC charger on the lithium side? I'm not worried about my alternator being able to fully charge the lithiums, I just don't want to overload the alternator and fry it while driving.

FYI: My 4- 235ah, 6V, GC AGMs work well, and aren't very old, it's the charging time that bothers me. When I have good sun it's no big deal, but when I have to charge with the generator it takes hours because as the batteries hit 85-90% of charge the input amps really drop. I'm looking at lithium mostly because they are fine with higher charge rates which will not only reduce generator time, it will also charge quicker from my solar which is better in the winter when there less solar hours.
Tom and Pris Masterson, w/ Buddy the 18 year old Siamese cat.
1998 Serengeti 3706
300hp Cat 3126, Allison 3060
900 Watts of Solar
17cf, Fisher & Paykel residential Refrigerator
Dragging four telescopes around the US seeking dark skies.
TDJohn
Posts: 552
Joined: Sun Oct 27, 2019 11:34 pm

Re: Charging Lithium batteries with stock alternator

Post by TDJohn »

Tom,

I would suggest to use a dc to dc charger that has the capability to charge Lithium. Lithium batteries are very low resistance and would put a very heavy load on the alternator, creating a lot of heat, which drastically shortens the alternator life, if it does not out right fry it from the get go.
Below is a link to a reasonably priced Renogy 60amp dc to dc charger. It is simple and, light and works very well. They also make a 40 amp and 20 amp models too for less money, this would also allow you to eliminate the diode based isolator. One thing I do recommend is to use a magnifying glass to set the dip switches, and to pay attention to the marking and position that the switches need to be in for the battery chemistry type you will have. A trucker friend of mine has one in use for 2+ years, used on a daily bases to charge four Crown 6V golf cart CR260 (amp/hr) batteries and it has worked flawlessly.
The charger is activated by an input from ignition power, but I recommend to still install a switch that feeds off of the ignition circuit. This way if you are stuck in traffic or your alternator dies, you can choose to turn the charger off. They also have a slow charge rate option that you can use via a second switch that lowers the charge rate to about 15 amps.

https://www.amazon.com/dp/B07Z4GSYC2/re ... UTF8&psc=1

What make and model inverter/charger do you have?

Some of the inverters/chargers get thrown off from the additional solar power you're getting in, even on cloudy days, and this would further prolong the top off charge, because the inverter/charger thinks the battery voltage is higher than it actually is. One thing you might want to consider if you decide to hold on to the AGM batteries a while longer, is when you have cloudy days, charge the batteries with the generator first thing in the morning, when you hit that 85% mark, shut the generator off and let the solar top the batteries off. On cloudy days the panels don't produce much amps, and the batteries at the last 15% SOC can't take much, so it usually ends up being a sufficient enough output to top off the batteries throughout the day, allowing you to reduce your generator run time. Considering that you have a residential refrigerator, it seems like your current battery amp hour capacity is marginal, not leaving much flexibility on the cloudy days, especially in the winter time.

As for Lithium batteries, one other advantage is the batteries won't be damaged or bothered if they are not topped off, so if you don't get topped off, but you have enough to get through the night, it eliminates necessary charging. Lithium batteries have the longest theoretical cycle life if they hover between 80 and 20 percent state of charge, only needing a full charge periodically for cell balancing, so if one has a decent amount of amp hour capacity, it allows for much more flexibility, reducing charge frequency considerably.
Right now it seems like the EG4 server rack Litium batteries are the best bang for the buck. You can get a 400amp/hr 12v battery for $1500. They have a very good quality BMS and are well built.

Are you going to be selling your AGM batteries if you decide to go Lithium? If yes, let me know what you want for them and what region of the country you plan on being this summer.
What brand are you AGMs?
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
Ozium
Posts: 9
Joined: Tue Nov 17, 2020 12:45 am

Re: Charging Lithium batteries with stock alternator

Post by Ozium »

Look for Blue Sea automatic charge relay to replace your isolator.
https://www.bluesea.com/products/7610/S ... 4V_DC_120A

While your at their website look through the catalog and the first pages have some setups that will work for you.

Pro marina catalog is good too.

http://www.delzer.com/oneasg/mbl_cat_003/

MasterVolt has a all in one solution and the batteries.

https://www.mastervolt.com/powerbook/en/
astrnmrtom
Posts: 167
Joined: Thu Oct 31, 2019 8:49 pm

Re: Charging Lithium batteries with stock alternator

Post by astrnmrtom »

Thanks for the info. That confirms what I thought. I have read some conflicting info as to the Leece Neville alternators being able to handle high output for long periods of time. I figured the safe way to go was a dc to dc charger, and I have looked at the Renogy 60amp dc to dc charger. That way I wouldn't take a chance on frying the alternator. 60 amps would be plenty while running the engine.

I have 4 - 235amp hour VmaxTanks 6V Xtreme AGMs purchased in 2020. They've worked well up to this point doing some occasional boondocking, but I feel charging them with my generator when needed is quite inefficient due to that last 10% taking so darned long. In good solar conditions my 600 watts of solar can do it alone. At other times I will do a bulk charge with the generator in the am for an hour, and let the solar top them off. My Fisher and Paykell residential refrigerator is surprisingly efficient, drawing 10-12amps off the batteries when running. In crappy weather I'll charge them most of the way in the am, and top them off in the evening with the generator. If my batteries are topped off by 10pm, my battery monitor is registering about 83% at around 7-8am the next morning. Not only will lithium give me more capacity, if needed, topping them off before bed will take less gen time. Odds are with 400ah capacity, I might not even worry about topping them off at night depending of course, the quality of the solar at the time.

Before heading off to full time I swapped out the old Heart 20D inverter/charger for discreet components. A 3000watt pure sine wave inverter and a 100amp converter charger that does have lithium capability. I occasionally use a smaller 60amp charger with a portable generator and it too can charge lithium.

This coming fall and winter we are considering quite a bit more boondocking, but this summer I'm in one spot for two months so I have the ability upgrade my system. First, I'm adding two more panels bringing my total to 900watts of solar and now I see lithium batteries at more reasonable prices than just a few years ago, so this is the time to upgrade if I'm going to. Depending on battery dimensions, I'll be going with 400ah if they'll fit in the existing battery tray. I figure with 900 solar watts and 400ah of lithium, boondocking will be quieter and I won't be so uptight with trying to conserve every amp of usage. No/less generator time will make my wife happier too. She hates the noise.

If I decide to go lithium, yes, I will be selling the AGMs. I'm in Northwest Washington state for the summer and right now I have no idea what I be asking for them.
Tom and Pris Masterson, w/ Buddy the 18 year old Siamese cat.
1998 Serengeti 3706
300hp Cat 3126, Allison 3060
900 Watts of Solar
17cf, Fisher & Paykel residential Refrigerator
Dragging four telescopes around the US seeking dark skies.
TDJohn
Posts: 552
Joined: Sun Oct 27, 2019 11:34 pm

Re: Charging Lithium batteries with stock alternator

Post by TDJohn »

With you adding two more panels and upgrading to 400 amp/hrs of lithium battery bank, you should not have any issues at all. Probably the hardest thing will be to re-gear your mind away from lead acid chemistry to the lithium chemistry. If you know how much amp/hrs you consume overnight w/o any late night charge, you can safely let the lithium bank get down to 15% w/o doing any harm, and with 400 amp/hrs, that should give you quite a bit of cushion without having to worry. And if you are that worried, you could give it only a half hour quick charge to make it through the night, as the lithium does not require to be fully charged at all.
For the time being, topping off late in the evening is about as inefficient way of charging as one can get. If you are at 83% SOC in the morning with a top off, it sounds like you can easily make it through w/o a top off. Even if you dip down to 40% SOC, as long as you fully charge the next day or two, it not a big issue as many obsessively claim. If it is done everyday, yes, it can shorten the life cycles by a little bit. Also, being that you have AGM batteries, they are much less prone to sulfating compared to flooded lead acid batteries. So on those poor solar days, you could easily bulk charge in the morning, as you do, let the solar top them off and then leave them to carry you through the night, even if they dip a little low.
Using a small portable generator is a much more efficient way to charge the batteries compared to the large thirsty propane generator. Another useful tip, if you have not thought of it, is if your residential refrigerator is the frost-less (defrost cycle) type of unit, set the defrost cycle to kick on in mid to late morning when you will have good solar and/or be running your generator on the poor solar days. The defrost element will pull some good amps, so it is best to avoid it during the night.
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
CactusTwo
Posts: 70
Joined: Mon Oct 28, 2019 12:06 pm

Re: Charging Lithium batteries with stock alternator

Post by CactusTwo »

With my 840watts of solar and 600ah of new lithium batteries, as soon as I "top off" the batteries in the morning, I heat the hot water tank thru my inverter and 120volts and then I turn on the refer to 120volt electric for the next 1/2 of the day light hours. Ma Nature does me good and I can say I use solar "to heat my water and cool my refer" but REALLY not for long or all day for sure. Extra pennies in my pocket for the box of beer!
Len and Brenda Nugent
Alberta, Canada, fulltimers since 2012
1996 Safari Serengeti 3740 front door, bought in Feb 2019
Cat 3126 300hp, Allison MD3060, VelvetRide suspension
sold 2008 GMC Duramax 3500 and 37' Cedar Creek 5th wheel
astrnmrtom
Posts: 167
Joined: Thu Oct 31, 2019 8:49 pm

Re: Charging Lithium batteries with stock alternator

Post by astrnmrtom »

Good info, thanks.

Yes, the late evening top off is what drives me nuts. Some generator time in the am is fine because I can make my coffee and toast if I want. Plus, with the batteries accepting more amps I don't feel the need to run it very long. With the lead acid batteries I get wound pretty tight about SOC and power usage even though I have some reserve. I know my wife would like it better too because she wants camping, even boondocking, to be as "normal" as possible. While she does get into boondocking mode, and is good about avoiding high draw appliances like the microwave, she forgets and leaves other things turned on and gets a little annoyed when I go behind her to turn things off. I know the AGM batteries can handle deeper discharge than I'm allowing, I just hyper focus on being as fugal as possible. These batteries were pricey so I do my best to baby them. Re: refer defrost cycles. Unfortunately I don't have any control over that cycle. I don't have any idea how often it defrosts but I have seen my battery monitor show about 26 amps every now and then and I suspect it's the defrost cycle. It doesn't seem to last long though. I did buy a timer for the refer to shut it off for a couple/few hours in the middle of the night to conserve even more, but have never tried it. With the extra reserve of lithium, I'd relax and stop meter watching.

The second thing that can be a potential issue that lithium would solve is using the Hurricane heater at night. When boondocking we use a Olympian Wave which doesn't require power but we've had a few nights where it struggled to keep the place warm. I'm fine in cool temps but again, my wife's comfort level is a good 10 degrees warmer than mine. Running the Hurricane doubles the draw on the batteries especially if it's cold. The refrigerator doesn't cycle often, but the Hurricane can, so while it draws about the same as the refer the total ah used per hours is greater.

Thanks to the Hurricane set-up I can have lots of hot water in the am without using any AC which is nice.

One thing that stopped me going to lithium when I upgraded my system for boondocking was the fear of lithium's temperature sensitivity. I've since read enough re-assuring reports that they aren't a sensitive as I once thought. Cold weather charging worried me more than hotter temps. I recently read about a person using 12v tank heating pads on a thermostat to keep that batteries at a chargeable temps. Another thing that has helped is two years of experience which has taught me that we won't be boondocking in extreme temps. What's more likely is chilly nights and early mornings.

Anyway, I'm still going a bit in circles over this decision because it's a pretty good chunk of cash to make the switch and the AGMs have worked up to this point. Since I'm in a campground for the summer I'm considering doing some driveway boondocking to get some better numbers. I'm thinking I'll unplug, let the solar do it's thing and skip the evening top off and see where I'm at in the am. I know winter will bring less watts and shorter solar hours but at least I'll have an updated baseline. I'm also kicking around the idea of doing a discharge test at the 20 hour rate to measure the true capacity of my batteries then I'll recalibrate my battery meter to the actual measured ah capacity instead of the advertised capacity plus a SWAG fudge factor like I'm doing now.

Thanks again for the info.

Tom
Tom and Pris Masterson, w/ Buddy the 18 year old Siamese cat.
1998 Serengeti 3706
300hp Cat 3126, Allison 3060
900 Watts of Solar
17cf, Fisher & Paykel residential Refrigerator
Dragging four telescopes around the US seeking dark skies.
TDJohn
Posts: 552
Joined: Sun Oct 27, 2019 11:34 pm

Re: Charging Lithium batteries with stock alternator

Post by TDJohn »

Tom,

Lead acid batteries have a rated life cycle, so partial or mini cycles will, to a degree, provide a bit longer calendar life, but total cycle life still adds up to be the same, unless batteries are abused. Meaning, they are left partially discharged for 5 days or more, some times weeks. That kind of abuse will shorten life quite a bit, but still less so on AGM batteries. People have been greatly misled by misinformation, wives tails/myths, that if one exceeds the magical number of 50% SOC their batteries will be irreparably damaged, the 50% mark is an ideal guide/goal, but not a must. True deep cycle lead acid batteries are designed to be able to handle up to 80% depth of discharge, meaning, a SOC down to 20% without damage. The key thing is to bring them to full charge at least every other day, preferably every day and not allow them to sit at that low of SOC for longer than a day. This is especially a non issue if these conditions happen only occasionally, that is why that cushion is designed in by the battery manufacturer. Believe me, these deep cycle golf cart batteries endure much more abuse in golf carts, being run flat multiple times a day and they still hold up and serve the industry very well. Some AGM battery manufacturers allow and/or recommend a mini/gentle equalize cycle (might be something worth checking into). If deep cycling is required and the manufacturer allows for gentle equalize cycles, it would not be a bad idea to equalize them every now and again, when there is plenty of sun, further prolonging battery life. This additional capacity, that people are lead to believe that it is not allowed to be used, would likely give you the needed amp hours to get you through the night, and allow you to give a good bulk charge in the morning with the generator, then topping off with solar. This additional cushion will very likely eliminate the need to charge at night, when it is most wasteful. Of course, worrying too much about usage and state of charge is not only stressful, but can drive your wife and yourself batty. ;) So testing the system while having the safety cushion of campground power is ideal. To simulate winter conditions, you could even turn your solar off around 3 or 4pm and see how many amp/hrs you draw overnight. I would not recommend doing an amp/hr test if it involves running the batteries flat. If your meter is off by a little bit, it's not a big issue. What brand is your shunt based battery meter?
As for the refrigerator, the defrost timer is not hard to find. It is either located under the cover of the cooling temperature settings or the front bottom section of the refrigerator, where the air intake is for the condenser coils and compressor.
The timer should look similar to the one in this link:

https://www.amazon.com/Refrigerator-Rep ... 5987&psc=1

The circle in the middle is the clock, just turn it until you hear a click and you will see the amps rise, do that around late morning. I have seen on some refrigerators where the timer is located by the temp dials, where it has an access hole to be able to adjust the time w/o taking the cover off.
If you don't feel comfortable with making those adjustments, you can choose to set your timer to go on for 20 to 30 minutes, once or twice during the night. That would be plenty to keep things cold, as these new units are very well insulated.

Have you eliminated phantom drains like the sound system, microwave, etc.?
For an example, my microwave draws a whopping 7 amps just sitting idle, doing nothing. I have connected through a power outlet bar and switch it on and off as needed, same with the TV/sound system. If you don't want to fuss with turning those items on and off, you could opt to put them on timers to go off around the time you retire to bed for the night. These are all various ideas to consider if you have a lot of phantom drains, and they do add up.

As for the Olympian heater not keeping up. Have you considered an electric blanket for your wife? They don't draw that much, especially the 12v units. Once your warm, it can be dialed down to a low setting, so the power usage is minimal. Saving on power and on pricey diesel fuel.

As for battery compartment. I know a few members who have built a battery tray in the engine compartment and moved the engine batteries into the engine compartment, adding two additional batteries for the house bank. This option would allow you to have 600amp/hrs of lithium if needed.
Also, have you considered locating the lithium batteries in the rear section of the basement?
This would allow the batteries to stay above freezing, giving you peace of mind and keep them cooler in the summer. It would also allow you the flexibility to get the low cost, but high quality EG4 server rack batteries installed. Each battery is 400 amp/hrs for $1500, so for $3K, you could have 800 amp/hrs and get rid of all your worries. BTW, those server rack batteries just got their UL listing, so good bang for the buck. If your inverter is strong enough, with 800 amp/hrs, you could run one a/c unit during the day, with long summer sun hours, you should have no issues.
All ideas to further muddy the lithium waters. :mrgreen:
If you do intend to keep the batteries in the exposed original battery compartment, make sure that the battery brand that you do go with, truly has low temperature cutoff for the battery charging (many brands claim they do, but actually don't), otherwise irreparable damage can occur if the batteries are charged bellow freezing temps.
Something else to consider if the lithium batteries are exposed to the cold elements, even with cold weather protection and pad heaters. If you happen to get caught on one of those polar vortexes, like people did in TX a couple of years ago, it might now be enough to keep your batteries warm to allow a charge, potentially putting you in a difficult situation. So maybe insulating or enclosing the battery compartment or getting some kind of thermal blanket for those extreme weather conditions that you may bump into. This way the pad heaters could keep up if it is very cold and windy to boot.

What brand and model charge controller are you using?
What wattage solar panels do you have, and are they connected in parallel or series?
During peak sun, under peak load, what is the maximum amp output from your solar charge controller are you seeing on your battery meter?
John
'95 Serengeti, Cummins C8.3-300
Allison 6spd.
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