Batteries not charging as expected

[DShK]

Problem child here again. I recently started to get back on the cut after the worst of the winter. I noticed my batteries weren't charging quite how I would expect. I have a bank of 6 6V batteries (and a starter that connects via smartbank). Some might remember a previous thread where they were gassing badly. I did not replace them in the end as they did stop gassing so badly. Basically, the voltage isn't getting as high as I would expect under charge. I started to notice this after my inverter charger would not turn on one morning (it eventually did after much crying in it's direction). In absorption mode, the voltage is not getting higher than 13.98V (measuring 13.88V on the batteries directly weirdly) absorption value is set to 14.4v. The charge current is correspondingly dropping off quite quickly. I wondered if my battery terminals needed a clean, so I removed all the corrosion and cleaned them up thoroughly - no difference. Oddly I got a bit of a shock/sparks when screwing a terminal back down (I chalked this up to my hands being covered in vaseline).

 

One pair of the series batteries is unbalanced, by about 0.15V. I think one of them is dragging the other down, and funnily enough this is the one that had the most corrosion on it. I don't know if this is causing the charging issue, but either way I think this needs to be rectified? Is one of those victron balancers the way to go? 

 

What might be causing the charging issue? (Or have I go something wrong?) My inverter charger is a Mastervolt Ultra Combi. I am leaning towards it not being the charger, as I get a similar thing through my solar - a weird charge profile. This goes from 12.2V straight to 14V, then down to 13.3V (float is set to 13.7V). It feels like the voltage is being pulled down by 0.3-0.4V, but this immediate rising and immediate dropping of voltage also looks odd to me....

 

Any ideas? Thanks!

 

[Tony Brooks]

Typically, the higher the current from a charge source the lower the voltage it will deliver so it may just be that the batteries are well discharged or have internal shorts. However, I am far from sure if this applies to the solar and mains charger because \i don't know their circuits. Wait for other peoples input.

[rusty69]

7 minutes ago, DShK said:

What might be causing the charging issue?

A knackered battery. Have you tried taking two of them out of circuit?

[DShK]

5 minutes ago, Tony Brooks said:

Typically, the higher the current from a charge source the lower the voltage it will deliver so it may just be that the batteries are well discharged or have internal shorts. However, I am far from sure if this applies to the solar and mains charger because \i don't know their circuits. Wait for other peoples input.

Well, currently they are sitting at 20amps at 14V, so not a huge amperage. My understanding is that bulk phase it will keep increasing the voltage to keep the current constant. So you would think it would be at the set voltage by absorption phase, especially when it's dropped down to 20amps in. I'm plugged into shore power. The batteries were down to 12V last night, and they haven't been on charge long - The charge rate fell off very rapidly from 100amps. 20amps does seem to be where it's liking to be charging at.

 

2 minutes ago, rusty69 said:

A knackered battery. Have you tried taking two of them out of circuit?

I have not, that does sound like a good next step. I assume if one is knackered, given they are 4 years old, I would want to replace the entire bank to avoid an unbalanced bank?

[BEngo]

If one is knackered, assuming they are all of similar age, then the rest will not be far behind.  Given the usual fun and games that replacing batteries involves I would do them all if you  can afford it in one hit.

 

N

[rusty69]

34 minutes ago, DShK said:

Well, currently they are sitting at 20amps at 14V, so not a huge amperage. My understanding is that bulk phase it will keep increasing the voltage to keep the current constant. So you would think it would be at the set voltage by absorption phase, especially when it's dropped down to 20amps in. I'm plugged into shore power. The batteries were down to 12V last night, and they haven't been on charge long - The charge rate fell off very rapidly from 100amps. 20amps does seem to be where it's liking to be charging at.

 

I have not, that does sound like a good next step. I assume if one is knackered, given they are 4 years old, I would want to replace the entire bank to avoid an unbalanced bank?

Very possible. I guess you have checked the obvious electrolyte levels. 

 

I would likely disconnect two at a time and see if any pair hold a charge with a load on. If you still have 4 good ones, you may be able to limp on until the solar season kicks in. 

 

Then you have the joyous lithium conundrum to consider. 

Edited February 14, 2023 by rusty69

[Tony Brooks]

1 hour ago, DShK said:

Well, currently they are sitting at 20amps at 14V, so not a huge amperage. My understanding is that bulk phase it will keep increasing the voltage to keep the current constant. So you would think it would be at the set voltage by absorption phase, especially when it's dropped down to 20amps in. I'm plugged into shore power. The batteries were down to 12V last night, and they haven't been on charge long - The charge rate fell off very rapidly from 100amps. 20amps does seem to be where it's liking to be charging at.

 

 Forget am the unbalanced bank, that would be very hard to achieve with LA batteries in good condition and good interlinks.

 

I expect both your solar and charger are doing adaptive charging, where the time in absorption (and possibly bulk) is guessed at and determined by voltage rise over time. It may well go into absorption, and the float long before it should for optimum charge.

 

Much of that 20 amps could be leakage through shorting cells. If any cells are hotter, dryer of gassing, when under charge, more than the rest, then it is a fair indication of shorting cells.

 

 

[DShK]

1 hour ago, rusty69 said:

Very possible. I guess you have checked the obvious electrolyte levels. 

 

I would likely disconnect two at a time and see if any pair hold a charge with a load on. If you still have 4 good ones, you may be able to limp on until the solar season kicks in. 

 

Then you have the joyous lithium conundrum to consider. 

Yeah I checked and topped up the electrolyte levels recently. I have considered lithum - I was looking at doing a setup with a B2B charger, but I got a bit spooked by someone saying you needed more complex systems to protect them than just the BMS. I might contact that four counties marine guy and see what he reckons an install might cost. I want to overhaul my electric setup soonish anyway. 

5 minutes ago, Tony Brooks said:

 Forget am the unbalanced bank, that would be very hard to achieve with LA batteries in good condition and good interlinks.

 

I expect both your solar and charger are doing adaptive charging, where the time in absorption (and possibly bulk) is guessed at and determined by voltage rise over time. It may well go into absorption, and the float long before it should for optimum charge.

 

Much of that 20 amps could be leakage through shorting cells. If any cells are hotter, dryer of gassing, when under charge, more than the rest, then it is a fair indication of shorting cells.

 

 

The unbalanced pair is nothing to worry about? Good to know. I think the adaptive thing makes sense. For whatever reason the voltage is spiking really quickly, so I guess it's thinking it needs to go into "absorption" mode quickly? It's already hit float - 13.3V (not high enough) and only putting in 0.4amps into the batteries. They were down to what, 40% last night, and I only plugged them in at about 11am, and spent most time charging at <20amps....

 

There's definitely one battery which was more corroded and I *think* had lower electrolyte levels. So I will try and remove this pair as a next step. I have to drive to scotland tomorrow for a job interview and I'm doing an art test today, hopefully nothing untoward happens while my mum boat sits 😂

[Alan de Enfield]

17 minutes ago, DShK said:

There's definitely one battery which was more corroded and I *think* had lower electrolyte levels. So I will try and remove this pair as a next step. I have to drive to scotland tomorrow for a job interview and I'm doing an art test today, hopefully nothing untoward happens while my mum boat sits 😂

 

Don't panic, but if you have a battery with an internal short you should isolate it immediately - do not leave it on charge it can explode splattering battery acid all around the engine bay (or wherever the batteries are).

 

I was woken in the middle of the night by the CO alarm - long story short - I was minutes away from a battery explosion, The battery had gone 'rugby ball shaped' and was so hot I could not touch it, the terminals were so hot that the spanner became too hot to hold, but by wrapping it in my shirt I got long enough to disconnect the links.

 

The battery was still too hot to lift out of the box the next morning.

 

If leaving your Mum 'boat sitting' make sure that the batteries cannot get any charge from Solar, a battery charger, or from the alternator.

You really should get the battery links disconnected. before leaving the boat.

Edited February 14, 2023 by Alan de Enfield

[DShK]

1 minute ago, Alan de Enfield said:

 

Don't panic, but if you have a battery with an internal short you should isolate it immediately - do not leave it on charge it can explode splattering batteru acid all around the engie bay (or wherver the batteries are).

 

I was woken in the middle of the night by the CO alarm - long story short - I was minutes away from a battery explosion, The battery had gone 'rugby ball shaped' and was so hot I could not touch it, the terminals were so hot that the spanner became too hot to hold, but by wrapping it in my shirt I had long enough to disconnect the links.

 

The battery was still too hot to lift out of the box the next morning.

 

If leaving your Mum 'boat sitting' make sure that the batteries cannot get any charge from Solar, a battery charger, or from the alternator.

You really should get the battery links disconnected. before leaving the boat.

 

I remember you regaling me with this terrifying story when I had the gassing issues! I still see no bulging (although there isn't any space for movement in the box) and haven't notice any heat. I think you're right, it will be prudent to isolate all charging while I'm away, even if I have time to isolate that suspect pair.

[Tony Brooks]

19 minutes ago, DShK said:

Yeah I checked and topped up the electrolyte levels recently. I have considered lithum - I was looking at doing a setup with a B2B charger, but I got a bit spooked by someone saying you needed more complex systems to protect them than just the BMS. I might contact that four counties marine guy and see what he reckons an install might cost. I want to overhaul my electric setup soonish anyway. 

The unbalanced pair is nothing to worry about? Good to know. I think the adaptive thing makes sense. For whatever reason the voltage is spiking really quickly, so I guess it's thinking it needs to go into "absorption" mode quickly? It's already hit float - 13.3V (not high enough) and only putting in 0.4amps into the batteries. They were down to what, 40% last night, and I only plugged them in at about 11am, and spent most time charging at <20amps....

 

There's definitely one battery which was more corroded and I *think* had lower electrolyte levels. So I will try and remove this pair as a next step. I have to drive to scotland tomorrow for a job interview and I'm doing an art test today, hopefully nothing untoward happens while my mum boat sits 😂

 

I did not say an unbalanced pair is nothing to worry about. I said it is difficult to get LAs in parallel unbalanced. In this case, "unbalanced" is your word, not mine, and I want to know how you know they are unbalanced and what you mean by that. A string of lead acids connected in parallel will self balance once charging is stopped . pairs of LAs in series might get themselves  unbalance, but as soon as you parallel another pair they should self balance (I think). This all depends on what you are talking about, but it sounds as if you may well have shprting cells.

[DShK]

7 minutes ago, Tony Brooks said:

 

I did not say an unbalanced pair is nothing to worry about. I said it is difficult to get LAs in parallel unbalanced. In this case, "unbalanced" is your word, not mine, and I want to know how you know they are unbalanced and what you mean by that. A string of lead acids connected in parallel will self balance once charging is stopped . pairs of LAs in series might get themselves  unbalance, but as soon as you parallel another pair they should self balance (I think). This all depends on what you are talking about, but it sounds as if you may well have shprting cells.

Ah sorry, I misconstrued what you were saying. Basically a multimeter across the terminals of one battery in a pair that are connected in series (6v batteries) is 0.15v different from the other battery. The combined voltage is I believe balanced, it's just there's a difference between the two in the pair. My understanding of this problem is that one will get overcharged - this is also the battery with the corrosion so in theory could be why it was gassing/corroding?. Which obviously isn't good, and I think can be solved with a balancing unit - but I'm unsure if this is indictive of a problem with that particular battery.

Edited February 14, 2023 by DShK

[Tony Brooks]

27 minutes ago, DShK said:

Ah sorry, I misconstrued what you were saying. Basically a multimeter across the terminals of one battery in a pair that are connected in series (6v batteries) is 0.15v different from the other battery. The combined voltage is I believe balanced, it's just there's a difference between the two in the pair. My understanding of this problem is that one will get overcharged - this is also the battery with the corrosion so in theory could be why it was gassing/corroding?. Which obviously isn't good, and I think can be solved with a balancing unit - but I'm unsure if this is indictive of a problem with that particular battery.

 

I think that I need to leave this to the ex GPO bods who dealt with large banks in series parallel. I think that you might be confusing lithium battery and Lead acid battery needs.

[DShK]

I could well be - I sometimes fly DIY racing style drones - you have to be careful about cell balance with those or you can get a nice fire. And of course those are LiPo battieres.

[cuthound]

Sounds very much like one or more shorting cells to me. 

 

Lead acid cells can only be "unbalanced" by differing resistances in the interconnects or by faulty (shorting) cells 

 

I would check to see if any cells feel warmer than the others, then remove the interconnects and measure the individual cell voltages. If any cells are faulty they will show a significantly lower open circuit voltage.

Edited February 15, 2023 by cuthound
Phat phingers

[Tony Brooks]

23 minutes ago, cuthound said:

Sounds very much like one or more shorting cells to me. 

 

Lead acid cells can only be "unbalanced" by differing resistances in the interconnects or by faulty (shorting) cells 

 

I would check to see if any cells feel warmer than the others, then remove the interconnects and measure the individual cell voltages. If any cells are faulty they will show a significantly lower open circuit voltage.

 

Especially if left disconnected over nigh or longer before measuring.

[cuthound]

1 hour ago, Tony Brooks said:

 

Especially if left disconnected over nigh or longer before measuring.

 

Indeed, the longer the cells are left before measuring, the greater the difference between normal cells and those being discharged by their internal shorts.

[DShK]

Interestingly enough this morning the solar was reading a proper float voltage, where it didn't before. I did notice the inverter charger making more of a noise than it used to (kind of a coil whine), so wondering if it's this not the batteries. Disconnecting the batteries as you guys mentioned sounds like a good plan - think I need to investigate if the inverter charger is still struggling to charge too. Will take a look when I'm back at the boat. Thanks guys!

[ditchcrawler]

1 hour ago, DShK said:

Interestingly enough this morning the solar was reading a proper float voltage, where it didn't before. I did notice the inverter charger making more of a noise than it used to (kind of a coil whine), so wondering if it's this not the batteries. Disconnecting the batteries as you guys mentioned sounds like a good plan - think I need to investigate if the inverter charger is still struggling to charge too. Will take a look when I'm back at the boat. Thanks guys!

If you have shorted cells the charger will probably struggle

[DShK]

I haven't had a chance to disconnect any batteries (I've been keeping an eye on them though). But I am seriously wondering if it is actually the batteries. Both the alternator and solar seem to have no problem getting them to the correct voltage (and also not flipping onto float super early). Which makes me think the charger is faulty somehow? Has anyone heard of this kind of problem before?

[DShK]

I am getting a terrible squeeling coil whine from the Mastervolt unit (it's not the fan). It didn't do this before. I wonder what is going on with it 😕

[DShK]

I contacted sellweb who repair these types of units. They think it sounds like the unit has developed a fault. About £500 to repair.

 

The question is what do I do about the electrics in the meantime? The solar is not yet strong enough to keep the batteries topped up and I need mains to work. Perhaps for mains I can get an extension lead with an rcb built in, to use in the marina?

[Alan de Enfield]

4 minutes ago, DShK said:

The question is what do I do about the electrics in the meantime? The solar is not yet strong enough to keep the batteries topped up and I need mains to work. Perhaps for mains I can get an extension lead with an rcb built in, to use in the marina?

 

Presumably :

 

a) If you are using a batterycharger (combo) then you already have a mains (marina) supply ?

b) Your boat already has a 'blue plug' that you connect the shore power into

c) Your boat has a mains circuit 

d) You can just plug your 'mains stuff' directly into one of your 3-pin plugs

 

For battery charging just get a cheap 5 amp charger from Halfords (other stores available) and plug it into one of your 3-pin plugs and charge the batteries

[DShK]

Cheapo charger is a good idea. I have one in my van for it's leisure battery actually. It's not got a very high current rating, hopefully it doesn't blow up!

 

Re mains. My "blue" plug goes into my inverter charger. It handles the switching between inverter and shore, hence without it I have no place for the mains to go.

 

I was thinking something like this as a temp measure might work/be safe?

 

 

https://www.jacksonsleisure.com/caravan/electrical/mains/hook-up/maypole/5-in-1/

[Tony Brooks]

It will if you have the money, but I suspect a length of cable, blue connector and a 13A wander socket would be cheaper. The shore bollard should have a MCB & RCD for protection.