Solar charging the starter battery
- Thread starter vomhorizon
- Start date
vomhorizon
Active member
Thanks! With the AGM battery I make it a point to charge it with AC power on a fairly regular basis. I also carry a lithium jump start with me when on long trips. With a lithium solar generator as a backup, I only envision straining my starter battery very rarely. I can always disconnect the fridge from the car battery and run it off of the lithium overnight and then charge both systems up in the morning. In the worst case, I would need to upgrade to a Group 27 from my current Group 34.
vomhorizon
Active member
I considered having a 75 AH Lithium auxiliary battery in the engine bay. But I don't anyone who has been running that for long enough to judge what the impact is on performance and life. Plust, They are too expensive at the moment to experiment with for me. I've just concluded that Lithium, for now, is best kept inside and a solar generator is something that I can use outside as well.
dreadlocks
Well-known member
sounds like your taking great care of it and it should always have a good charge state, but without any kind of battery monitor in it the problems will likely start being an issue long down the road when your starter battery is on its last legs.. I've gone out with a battery that would start the vehicle but not run the fridge any time before my LVD cut out, was able to dump a bunch of amps fast but any steady loads just crashed its voltage after a few mins.. the LVD is kinda a crutch for the fact you dont have a battery monitoring system, it will do its thing automatically incase your assumptions on the current state of the battery are incorrect, ideally you never want it to trigger.. I know the first time mine did I was super confused, until I remembered I had installed it and checked it out.. then it was oh crap my battery just bit the dust out on me in middle of 2 week trip.
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OK with your LI powerpak (let's please abstain from that silly use of the term generator)
that in effect becomes your House bank.
A nice big say 200-300Ah LFP pack could probably get shimmied into where your big lead Starter is mostly wasting space.
As I said you might only get 2000 deep cycles and 8yrs due to the heat rather than 8000 and maybe decades, but hey it's only money, maybe 2 grand?
Just do not expect much total capacity otherwise, I assume you're not carrying even a tiny gennie?
Usage like 20-30Ah per day is probably at the top end, unless you are driving every day with a good DCDC of your alternator refilling your House powerpak.
that in effect becomes your House bank.
A nice big say 200-300Ah LFP pack could probably get shimmied into where your big lead Starter is mostly wasting space.
As I said you might only get 2000 deep cycles and 8yrs due to the heat rather than 8000 and maybe decades, but hey it's only money, maybe 2 grand?
Just do not expect much total capacity otherwise, I assume you're not carrying even a tiny gennie?
Usage like 20-30Ah per day is probably at the top end, unless you are driving every day with a good DCDC of your alternator refilling your House powerpak.
vomhorizon
Active member
I don't need 200-300 Amp Hours of Lithium. I don't have anything drawing that would warrant much capacity and do not intend on being out remote for weeks at a time where the cumulative impact of draw-replenish warrants such a large bank. The biggest draw (when camped) will be from an Engel 40 Liter fridge and a couple of camping lights. I can always switch the fridge to the lithium bank at night and charge it up when driving during the day (or using the solar panel when camped).
Yes that fridge is very efficient, but you really should get at least a cheap Ah counting wattmeter if not a proper battery monitor
in hot ambients keeping the temp dialed down it would be easy for your outgo to exceed your income
and you really don't have much buffer.
Be sure to regularly test your backup jumpstarter to avoid getting stranded.
in hot ambients keeping the temp dialed down it would be easy for your outgo to exceed your income
and you really don't have much buffer.
Be sure to regularly test your backup jumpstarter to avoid getting stranded.
67cj5
Man On a Mission
Depending on the Ambient Temp your Fridge can chew up to 60Ah per day and if you own a snomaster that is a common event, Being an Engel it can chew as little as 9.5Ah per day in cooler weather and up around 45Ah+ on very hot days, So if you are travelling in Hot areas you would need a minimum of 2X 80Ah Deep Cycle batteries just to have a Buffer for those times when you don't get a chance to recharge your batteries 2 or 3 days in a row.
vomhorizon
Active member
Thanks! This is a very handy range for me to consider as I build it up. I don't plan on leaving my fridge permanently mounted in my rig when it is being used as a daily driver. We usually get to camp in late afternoon and are usually out on a trail etc for most of the day. So late afternoon and the morning is when the car is likely to be stationary and the solar chargers working to charge up the starter battery. At night is when the fridge will be working without the alternator. That's probably when I need to substitute via a " house-battery". For now, that will be a 40 Ah portable lithium unit (there are a few that fit in my drawers nicely) and we could always scale that or add more solar. The longest we are ever out completely away from any opportunities to charge via AC is like 5 or so days. I think between the 100 W solar panel, a Group 27 battery, and a 40 Ah portable unit we should be fine. If not, I can consider adding more portable lithium or having a dedicated solar charger for it.
67cj5
Man On a Mission
Well I have a few options in place, I have 3X 110Ah Deep Cycle batteries which are great if I can park up and set up the Solar panels all day and for when I am on the move I have 2 Dometic PLB-40 Lithium Packs that will run the fridge all night and will charge up as soon as I hit the road within 1 to 2 hours Max,
When using the 3X 110Ah batteries I have a 2000w Generator that powers a 38A Charger which can put enough power back in the Batteries while cooking Breakfast having Coffee and doing the dishes, LOL. "!'m trying to be House Trained"
PS, If you only want to run small things like battery Chargers an 800w Generator is more than man enough because a 40A charger will only need about 200 to 350w of power at the MAX and where they run for around 5.5 hours on half a gallon of Gas at 3/4 load because they are only powering a battery Charger they will run in excess of 10/12 hours easy so 20L / 5 US gallons is going to run the little generator at leased 40 or 50 hours or more.
During the day I can plug the PLB-40 in to the Cigar Socket while travelling at the same time the Fridges are plugged in to the PLB-40's So really the fridge is being powered by the Alternator So the PLB-40 only has to run the fridge at night and If needed I can Charger the PLB-40's from the Cigar socket or Direct from Solar or from the Generator So I got all bases covered and the Van has it's Own 80Ah/800cca Starter Battery and if that goes Flat I have the G15000 and the G26000 Noco Chargers as well as the Noco GB150 Booster and the Noco GB40 So I got enough to power a small house,
As an added extra my Camper conversion came with a small independent Lithium setup just for lighting and Phones etc, So all up I have about 5 separate power sources Plus I have solar powered lighting that I stick to the Vehicle at night via magnetic Tape,
Bottom line is there loads of ways you can have extra power without having to mess with the Vehicles electrics,
Anyways I hope that helps,
DaveInDenver
Middle Income Semi-Redneck
FWIW, I've recently been using a data logger to watch the voltage at my MT45, which is wired in the bed of my truck with about a 30 foot 8 AWG out and back loop to my batteries. This is example of an overnight with no solar helping. You can pretty much figure out the stages where I'm driving, stopped hiking, driving again to make camp, sleeping, making breakfast and driving home again. This occurred at a fairly high elevation so the overnight temperatures were on the low side of typical late spring/early summer. I think it peaked during the day in the mid 80s and dipped to about 45°F. I'd normally expect a couple more overnight cycles but generally this isn't an a wildly unusual duty cycle for me in the mountains. Down in the desert it cools off a lot too but that's going from 100°F to 65°F, so it's a much more difficult ambient environment all around.
Anyway, the data logger I have for this can't be easily calibrated so the open circuit error compared to a known good DMM is 0.15 V low. The peaks are 14.2 V charging (this is an uncorrected Toyota alternator, e.g. no voltage bump diode installed), 13.9 V settled running.
The capacity of this battery is 65 A-hr and my fridge running is approximately 2 A. I expect less than 0.1 V of drop between the cable run, terminals, fuse block, etc at 2 A consumption, which calculates to a discharge rate of C/32.5 in this case. All told indicated here ~12.4 V should represent ~12.6 V at the battery inclusive of losses and instrument error. So ~12.6 V at ~C/32.5 discharge would mean somewhere around 65% to 75% state of charge after roughly 17 hours off the charger and no particular attempts made to maximize run time.
Point being doing this would probably still start the truck alright in a similar scenario as you present. Remember I have dual batteries where the actual starting battery doesn't get dragged down, so I can't say that definitely.
But I probably wouldn't push my 65 A-hr example to still start after two days without charging. This is why I built the solar for my single group 34, which is a similar capacity. That 100 W of solar did roughly offset the majority of daytime consumption and made a couple of mostly stationary days possible without too much worry unless it happened to rain all day.
vomhorizon
Active member
Thanks! I think upgrading to a Group 27 will serve me fine once I'm ready to replace my Group 34 (a transplant from my previous rig). And there is option for additional solar as well, beyond the 100 Watt panel I'll be putting up initially. Particularly if it could also charge the small lithium battery inside.
DaveInDenver
Middle Income Semi-Redneck
It should be noted that what I show here is fairly abusive on a starting or so-called dual purpose battery. They aren't built to do these little cyclic loads over long periods like a real deep cycle. If you do this often it does shorten their life and thus decreases replacement period and may increases total cost.
So I don't disagree with the brain trust on the proper way to approach this. I'm just presenting an argument that it's not absolutely necessary if you're modest in expected loads and stay on top of driving/charging and monitoring energy in-out/state of charge/voltage/something.
So I don't disagree with the brain trust on the proper way to approach this. I'm just presenting an argument that it's not absolutely necessary if you're modest in expected loads and stay on top of driving/charging and monitoring energy in-out/state of charge/voltage/something.
For sure any battery used for deep cycling (as opposed to dedicated to Starting only)
should be from a known - good maker and a model designed for longevity in true deep cycling usage.
Odyssey's PC-2150 is such, very rare in that it truly lives up in reality to the "dual use" label.
That's G31 size, they likely have others in that line.
should be from a known - good maker and a model designed for longevity in true deep cycling usage.
Odyssey's PC-2150 is such, very rare in that it truly lives up in reality to the "dual use" label.
That's G31 size, they likely have others in that line.