Battery Resting Voltage

[Lilla Hus]

Hi folks..
I've recently swapped out my Trojan lead acid batteries which were consistently dropping their voltage to under 12.2V overnight, for some reason. I was gifted three AGM marine 115ah, which were originally at 12.8V, but which have also been sat, some mornings at around 12.2V.
My victron shunt told me there was just above a 1amp draw somewhere, which I traced to my fridge relay and also my external cameras, which have permanently illuminated LEDs, even when not powered up, so to speak.
I eliminated these drains, but still the batteries sit between 12.2V and 12.4V with only a drain of 0.19a overnight.
Basically it means that I cant start the diesel heater in a mowithout first starting the van to charge the battery.

I'm wondering whether the amp draw that's present (see pic) ought to be able to drag my batteries down this far overnight
I'm also contemplating a move across to a lithium battery instead, but I'm not sure if I'm going to run into the same problem with that.
It doesn't seem feasible that both the lead acid and AGM batteries would be on their last legs..
Hopefully someone will be able to shed some light on whether my batteries are goosed and/or whether Lithium would help..
Cheers
Phil

 

[SquirrellCook]

I don’t think you’ve been charging them hard enough. My Trojan’s are not doing as well as I would like. They do like to spend a long time on absorption. I undercharged mine initially.

 

[Lilla Hus]

You're probably right, Squirrel, I drive a round trip of 20 miles to work each day with the DC/DC charging and the rest is left to the MPPT. To be fair, I'm only using the electrics on an evening if I'm tinkering as we're not full time yet.
Up until the Winter, the Trojans had been levelling back to 12.6V after an evening in the van, so the drop down to what's considered 50% with so little Ah out, was quite alarming.
I might have to consider extra charging methods or maybe splash for lithium.
Thanks for the reply

 

[SquirrellCook]

It does look like Lithium might be a better answer for marginal charging. To early to tell with mine, but I am toying with getting some more to replace my pair of Trojan's

 

[Nabsim]

You still need to charge lithium so don’t just jump thinking they will solve your problems (I run 2x 100ah Lifepo4 battery’s so not knocking them).
Something amiss as the deepest discharge is very little. You could fully charge with your b2b but need to run long enough to replace whatever is used as you know.
I would get the batteries out and give them a good charge with a decent charger for a minimum of 24 hours, preferably 48hrs to make sure they are properly charged then see what happens. If they still drop as low overnight with such a low discharge then they have definitely lost a lot of capacity. 12.2 isn’t too low but you don’t want to drop a lot lower

 

[Lilla Hus]

You still need to charge lithium so don’t just jump thinking they will solve your problems (I run 2x 100ah Lifepo4 battery’s so not knocking them).
Something amiss as the deepest discharge is very little. You could fully charge with your b2b but need to run long enough to replace whatever is used as you know.
I would get the batteries out and give them a good charge with a decent charger for a minimum of 24 hours, preferably 48hrs to make sure they are properly charged then see what happens. If they still drop as low overnight with such a low discharge then they have definitely lost a lot of capacity. 12.2 isn’t too low but you don’t want to drop a lot lower

I might have to look into a decent charger for when I need the batteries topping up a little more, Nabsim. I have a 30amp DC/DC and a 50amp MPPT, now, but if neither are getting a lot of power, then I'll have to look into the other options.
The main advantages I can see with lithium are that it charges quicker and also that it maintains that charge better. The cost is it's downside.
Thanks for the reply

 

[Nabsim]

Yes that’s the one advantage for me, how much charge I can put back in quickly. I don’t tend to move often enough and long enough to recharge my battery’s daily so I need to carry a generator. That keeps me going approximately five months of the year BUT I do use quite a lot of power (around 65 amps every 24 hours). With your deepest discharge figure it doesn’t look like you use that much

 

[Sprinter 1 cup]

I got 40wh from 200w of solar . 3days = 170watts

 

[SquirrellCook]

I got 40wh from 200w of solar . 3days = 170watts

Well done you sun seeker

 

[MarkJ]

I got 40wh from 200w of solar

Don't think it's actually got light here today. Black cloud and gloom all day.

 

[Lilla Hus]

It does look like Lithium might be a better answer for marginal charging. To early to tell with mine, but I am toying with getting some more to replace my pair of Trojan's

There's definitely one or two advantages to the lithium batteries, Squirrel.. I'll battle on with the AGMs for now..we're due away over the hols and time is short for changing things anyway.
I've just had a quick look at chargers and although they'll be great whilst we're still in the house, come April we'll be offgrid and back in the same situation next Winter..

Yes that’s the one advantage for me, how much charge I can put back in quickly. I don’t tend to move often enough and long enough to recharge my battery’s daily so I need to carry a generator. That keeps me going approximately five months of the year BUT I do use quite a lot of power (around 65 amps every 24 hours). With your deepest discharge figure it doesn’t look like you use that much

 

[Lilla Hus]

Yes that’s the one advantage for me, how much charge I can put back in quickly. I don’t tend to move often enough and long enough to recharge my battery’s daily so I need to carry a generator. That keeps me going approximately five months of the year BUT I do use quite a lot of power (around 65 amps every 24 hours). With your deepest discharge figure it doesn’t look like you use that much

Yeah, at the moment we're in the house and selling/reducing our possessions, so daily power usage is minimal, although the van is my daily drive. A generator would save you having to search for hook ups, I suppose and it may be a future option for us. I keep thinking that once the house is sold and we're living in the van, a charger would be mostly unused...but; it would sort the issue I'm seeing at the minute..lol