Newbie battery charger questions

[wallport]

Yes I guess I'm not taking into account that the starter battery has got a lot of stuff connected.

Whilst we are on the subject of charging the SB, looking through a lot of previous posts it looks like the ctek mxs 5.0 is a favoured product and I would combine with the cigarette socket adapter. Was just near to buying when the price went up though so might leave it and look for an offer.

 

[TallPaul_S]

Yes I guess I'm not taking into account that the starter battery has got a lot of stuff connected.

Whilst we are on the subject of charging the SB, looking through a lot of previous posts it looks like the ctek mxs 5.0 is a favoured product and I would combine with the cigarette socket adapter. Was just near to buying when the price went up though so might leave it and look for an offer.

You have a Victron charger for your LB, don't you? On hook up.

The Victron blue smart 12/5 is also an option, you can get a 12v socket adapter for them.

https://amzn.eu/d/irspwnv

Mine is currently sat on the driveway plugged into the hookup and charging the LB via the Victron 15a and the SB via the Victron 5a plugged into the 12v socket.

It also means I can (just about - the Bluetooth range on the LB charger isn't great!) monitor them both from inside the house via the app.

 

[wallport]

OK that's another thought and I like the bluetooth capability (WiFi would be even better). I would say though that I find the victron app in conjunction with my ip22 confusing - could do with time stamps.

Will check out the prices and relative dimensions though.

 

[roadtripper]

Set up a price alert in CamelCamelCamel if you want to snag the good Amazon prices, though it doesn't catch the voucher offers. The maintenance chargers from CTEK/NoCo/Victron all are good choices, the Victron makes sense to partner with your existing one but if you snag a good price on a CTEK or NoCo...

With a starter battery it's not so much the absolute voltage you want to worry about but it's ability to provide the big surge of current to start, so long as it's doing that you're fine.

 

[wallport]

Well it failed the test big time. No idea why it suddenly drops but that was with all fuses pulled and left completely untouched.

 

[TallPaul_S]

View attachment 239401
Well it failed the test big time. No idea why it suddenly drops but that was with all fuses pulled and left completely untouched.

So this was with all fuses removed, both chargers (once off charge) and all 12v items, correct?

What I'm seeing here is:

Stage 1. Storage charge on the Victron. 13.2v
Stage 2. Expected reduction of the voltage once the charge is removed, down to 12.6v

All good, up to there. It's once it hits 12.6v that it goes off a cliff, it's at below 12v in half an hour roughly! Then it's down to 11.5v which is basically 20% charge or lower, in 3hrs.



I think a new battery is due.

 

[wallport]

I suppose I could remove the battery terminal for one last test but I agree.

I suppose the next question is whether to replace like for like or a small upgrade (I won't go lithium). The battery compartment is a constraint as it only just fits the current battery (the bm2 only fitted due to the lower level of the slot which runs down each side of the battery although it could be velcro'd to the end instead (there are no ends to the compartment so slightly longer is an option but not higher or wider).

We will never be big off grid campers but a couple of nights would be good.

 

[TallPaul_S]

You're going to be constrained by space, so check that very carefully. If you can get a 110Ah to fit then no reason not to go for that.

Any reason why LiFePO4 isn't an option? I know a 100Ah is about £350 Vs £150 for a 100ah AGM, but then you are getting effectively double the capacity. You can get cheaper with the eco-worthy but that has no low temperature cut off and I don't think your CTEK has that function.

Although saying that, for a couple of nights off grid, even without solar an 100Ah AGM is fine.

 

[wallport]

Well, a bit worried about fire is I guess the main reason but I will do some reading on those. We have also considered getting solar fitted to the roof so I suppose the time may have come to decide on that and get both done or buy the right battery now for future compatibility.

 

[wallport]

I think we have concluded that my battery has had it but please could you bear with me and help me understand the victron app screens.
From that 11.5v status this morning at about 11am, I put it on charge and here are some screen shots.

So, cycles are always 30mins?
The screens showing the most recent cycles seem to change when you scroll right and then back again - does it not automatically refresh or something?
Does this all look right?
How long should I charge it before this very final test removing the battery terminal?

 

[TallPaul_S]

Nope, 30 minutes isn't right. It looks like the Victron is basically thinking the battery is almost full - it's going from bulk (less than 80%) to absorption (80-100%) to float (100%) to storage (100% but with no activity) in under 5 hrs. It's basically going from bulk to float in about 2 hours. Which would be fine if the battery was pretty much fully charged already. Bear in mind the charger will only be putting in the full 15a (so 15a of charge in an hour) on its bulk stage. But, it started the bulk cycle at about 11.6v, which would be around 20% full in a normal battery. So 20Ah of 100Ah. So to get to 80% or 80Ah, it would need to charge at 15a for 4 solid hours. Which it ain't!

80 - 20 = 60. 60 / 15 = 4.

 

[TallPaul_S]

Well, a bit worried about fire is I guess the main reason but I will do some reading on those. We have also considered getting solar fitted to the roof so I suppose the time may have come to decide on that and get both done or buy the right battery now for future compatibility.

The main thing you need to be aware of with lithium is to never charge when the batteries under 0 degrees C. A quality LiFePO4 battery with have a low temp cut off which will prevent charging below these temps, and may have a heater too which warms it up so you can charge when it's below freezing.

If you're thinking of going with solar, with no low temp protection it's too easy to have a bright winters day below zero and without protection, the batteries will charge.

So worth spending a little extra. You could get a 100Ah LiFePO4 which would have double the effective capacity of your 100Ah AGM, and would you run a 1000w inverter if you wanted to. Oh and they're about the size of a std 70Ah AGM battery, and half the weight.

 

[wallport]

Nope, 30 minutes isn't right.

Hmm - is there anything in my setup which behaves as expected? I'm sure it's always done 30minute cycles - there is a previous screenshot in this thread (19th Dec 23) which also shows this.
So, bound to ask, is there the possibility that the battery hasn't been charged properly before these tests?

 

[TallPaul_S]

Hmm - is there anything in my setup which behaves as expected? I'm sure it's always done 30minute cycles - there is a previous screenshot in this thread (19th Dec 23) which also shows this.
So, bound to ask, is there the possibility that the battery hasn't been charged properly before these tests?

I can see that, although there was one cycle which was normal:




The Victron app classes the charge cycles (I think) as bulk and absorption, which is the timer, and then maintain as float and storage.

So in cycle 7 as above, it did barely anything in the charge cycle (0.7Ah) but I'm guessing it was left on hookup for a few days and it put in 65Ah on that stage. Which seems a lot, as float and storage should only be when the battery is at 100%.

The 6hr charge in cycle 6 is much more what I'd expect from a fairly discharged battery, the charger added nearly 30Ah in the charge cycle, so 30% of the capacity.

I think the reason you're seeing a lot of 30 mins long charge cycles, is that the Victron minimum absorption stage (which is when the battery is about 80% full) is.... 30 minutes. So, every single charge cycle, regardless if the battery is (or thinks it is) 99% full, will be 30 minutes minimum, if it goes from bulk to absorption. And seeing as all your charge cycles are basically putting nothing into the battery, it's still doing the minimum 30 mins absorption stage, which is all yours seeing (plus 10 seconds of bulk!).

Have you left the battery on charge for long periods over winter? If there was a slight drain that could cause issues too. There's also things that can cause a jump in voltage after a short time on charge when the battery isn't actually full. Which might be what you're seeing.

Do you have access to another battery charger? Anything will do, even a cheap 5a car battery charger. Might be worth just connecting that up and seeing if it does the the same, IE going from bulk to absorption extremely quickly as the Victron is doing.

 

[TallPaul_S]

Here's my cycles from my SB charger, which regularly goes down to 12v or so. It's only a 5a so yours in bulk phase would charge 3x as fast.


I did have one 30 mins cycle which was I think when I unlocked the van while it was charging, that last but one cycle where it was on for 6hrs 15m, then when it started again it went start past bulk as the battery was basically fully charged, but it still had to do 30m minimum of absorption.




So, any of your 30 mins charge cycles where it's putting in basically nothing, it's only 30 minutes due to the 30 mins minimum absorption stage.

 

[wallport]

Do you have access to another battery charger?

No unfortunately not.

I think my whole charging history over winter is in this thread - how sad and boring is that.

A lot of recharging in the various tests investigating possible causes of drain but except fairly recently when it was on charge for 2-3 weeks, it has been a few days each time.

Could the knackered battery be fooling the charger into this behavior?

 

[TallPaul_S]

Could the knackered battery be fooling the charger into this behavior?

Yep.

It might be showing at fully charged, but if the capacity of one or more cells is done, then it might only at 1/4 capacity. What you might also be seeing is the surface charge, this depletes slowly down to 12.6v if there's no draw, and quickly if there is a draw. The battery might not be taking a charge and all the charger and BM2 is seeing is the surface charge.

 

[wallport]

Yep.

Ah that could be good in a way. Whilst I've probably got the expense of a new battery coming, at least a knackered battery could explain all the other issues and mean I'm only looking at one problem.
Could just do with 100% proof on the battery.

 

[TallPaul_S]

Ah that could be good in a way. Whilst I've probably got the expense of a new battery coming, at least a knackered battery could explain all the other issues and mean I'm only looking at one problem.
Could just do with 100% proof on the battery.

You can get it tested at various places, might be worth a try. Halfords do a free check but I'm not sure how good it is.

 

[ginkster]

Well, a bit worried about fire is I guess the main reason

The stories you hear about lithium battery fires are largely Lithium-ion batteries such as those used in scooters, vapes etc. A decent lithium leisure battery will be a LiFePO4 which is a far more stable and safer technology. Definitely worth reading up on the difference to allay your worries. Fogstar have a good post about it:

Li-ion vs LiFePO4

TallPaul_S has highlighted the many advantages they bring and things to consider (sub-zero charge protection is vital). I’ve recently swapped my leisure battery from 100ah lead-acid to a Fogstar 105ah LiFePO4 and it’s a game changer. 2/3rds the size, 1/3rd the weight, twice the usable capacity, can be run flat without killing it, charges faster, can be placed on its side, higher output so can run an inverter, 10+ year life….etc.

My old (knackered after only about 2 years) battery would run my fridge for about 24 hours, the Fogstar runs it for a week with capacity to spare!

From the info you’ve posted it certainly looks like your battery is knackered. I would thoroughly recommend the Fogstar as a replacement. Yes it costs a bit more but you will not be disappointed. And will spend a lot less time monitoring your battery!