Unable to Get a Full Charge

[Hugh Walker]

Hi all,

We've had a love/hate relationship with our charging system for a while now, actually just replaced the service bank (580Ah of trojan wet cells) 2 months ago and thought our problems would be solved, but predictably... no.

When we first installed the new service bank we tested them with our hydrometer and all were 100%. We've also had an electrician load test them recently and all passed. Since the first charge though we haven't been able to get the hydrometer above 50%.

I've been paying a lot of attention to the chargers and I feel they're switching into float mode too quickly before imparting full charge. Yesterday for example we tested with the hydrometer before charging (1.15) as soon as the chargers went into float (1.16) which was only 2 hours later and then after letting the chargers continue all afternoon and night (1.18). Unfortunately we're not in marinas often so can't do this regularly.

We also have a Xantrex Link Pro but I don't trust the readings because it synchronises itself on sensing the chargers in float and I don't think that's 100% charge. We do use it though for volts and Ah's used. What we do notice is a rapid decline in volts, for example 12.6 after charging to float and roughly 100Ah later the voltage will be somewhere around 11.9.

Our chargers are standard Beneteau set up, two Dolphin 40A chargers (one connected to service only, one connected to service, starter battery and bow thruster battery). We have noticed that once in float we can trick the chargers by turning them off then on again, this gives us another 30mins to an hour before they go into float again.

In regard to charging on alternator, it's not much different, the amps going in dwindles down to float level in about the same time as the chargers.

The same electrician who load tested the batteries also had a quick look over the whole setup and tested for resistance in a few place and didn't find anything he thought was wrong.

Anyone have any suggestions as to why can't we get a full charge?

[CharlieJ]

What model and how old are your chargers? Where any other changes made to your battery system when the new batteries were installed?

Our chargers are standard Beneteau set up, two Dolphin 40A chargers (one connected to service only, one connected to service, starter battery and bow thruster battery).

Although you call this "standard", it is a strange set-up as chargers use sensed voltage as their "trigger" for shifting from one charging phase to the next. Thus, with both chargers sensing, and responding to, the voltage on the service bank they will literally receive mixed signals.

That being said, it appears that you have a malfunctioning charger. As a first step at troubleshooting, suggest that you place Charger #1 on the service bank only and let it cycle a couple of times. Then disconnect Charger #1 from the service bank and place Charger #2 on the service bank only, and let it cycle a couple of times. If it is a charger issue, this relatively simple test will quickly id the culprit. Note that with many chargers with multiple (usually three) output channels, two of the unused channels have to be jumpered together or only Channel #1 is to be connected when charging a single battery or bank. Check your documentation for specifics.


Hope this helps.

[newboat]

A little more food for thought-the Dolphin chargers have a poor reputation. I think your regulator(s) sound like they are in the Dolphins and are regulating (incorrectly) your charging rates whether plugged in or alternator. If that is the case, it could be that your nice new batteries are not getting the charge they need and are acting accordingly.
Please keep posting as to how this pans out

[btrayfors]

Hugh,

The voltages and voltage changes after only 100AH draw are in-and-of-themselves enough to tell you that there is a serious problem.

You're right: the new batteries, like the old ones, are not getting a full charge. Moreover, it doesn't take many months at a partially discharged state to KILL YOUR NEW BATTERIES. You have to fix this problem quickly.

On the Trojan wet cells you should be seeing 14.6 to 14.8 volts during the bulk and absorption phases. Measure what you're getting with a good multimeter on the battery terminals, and on the alternator output.

The Link readings are virtually meaningless unless you've properly charged the batteries FULLY and recalibrated. And, while helpful sometimes the SG readings with the hydrometer are messy and potentially harmful (they may allow contamination in the battery, burn holes in your pants, etc.). Rather, depend on a good multimeter and a good clamp-on ammeter to give you reliable readings.

Again, although it may be painful to the pocketbook now, you've got to solve this quickly or your pocketbook is going to be even more depleted as the new batteries die an early death.

One of the first things you'll want to do after the batteries are fully charged is to do an equalization in hopes of knocking some of those lead sulfate crystals off the plates.

Bill

[Hugh Walker]

Thanks for the help so far everyone, here's an update.

We haven't been able to isolate the problem to just one of the chargers. The falling into float early seams to happen on both. We did take the chargers to a technician a couple days ago to be tested and he found nothing significantly wrong. He did increase the voltages slightly but didn't think that alone would be enough to fix our troubles. Currently we're in a marina ensuring a full 48 hours charge to see if we can't get them to 100% (we're manually resetting the chargers every few hours). I have also disabled the auto synchronizing on the Link Pro so hopefully we can watch the Ah's from now on.

Next normal cycle we're to monitor the volts and amps and write is all down for the technician to see if that can help him (actually won't be able to do this for a week because we've visitors right now), I'll post it here too.

Thanks especially for the warning of damage to the batteries, I think the next thing we're going to do is get a known working charger onboard to see if that will impart a proper charge.

[Hugh Walker]

Actually I've one quick question about reading voltages... ours seam to jump around a lot depending on the current, for example I'm looking at the volts now and the chargers are on, it reads 14.4V with no load but when the fridge cycles on with 4Amps the voltage drops down to 14.2V. Is this normal?

[btrayfors]

Yes, one often sees this. Depends in part where the voltage sensing is done.

BTW, you should be measuring voltages with a good digital multimeter at the terminals of the batteries and at the alternator output (positive) post.

Good luck.

Bill

[GeoPowers]

It doesn't make sense to me that it would be the charger if you are getting about the same results with charing using the alternator. Although having two chargers for the same bank seems odd also. Those batteries are very low according to your SG readings. My first thought would be that the chargers and alternator are getting a high voltage reading from somewhere else.

It sounds like you have 3 banks- start, windlass, and house. Is it possible that either the start or windlass batteries are fully charged, and the starter or alternator is sensing their voltage instead of the depleted house bank? I assume you have isolated the house bank with a bank selector switch. If this was my boat I would mechanically disconnect the house bank from everything except the charger and/or alternator and try to do charge them again.

Good luck!

Frank

[Hugh Walker]

Well I finally got around to doing some proper testing of the chargers and I've found an obvious fault with the second charger. As was suggested I observed each charger individually connected to only the service bank and took the below measurements. I can see the the 1st charger works pretty much perfectly and was still holding 14.2V after 240 minutes. The second charger starts the same way but after 30 mins it trips into float where it drops down to 13.2V (I discontinued measurements at this time).

1st Charger
Min Volts Amps
0 13.2 36
10 13.2 35
20 13.3 34
30 13.2 32
40 13.2 32
50 13.4 31
60 13.6 31
70 13.6 30
80 13.8 30
90 13.9 28
100 14.0 26
110 14.0 22
120 14.1 18
130 14.2 17
140 14.2 15
150 14.2 14
160 14.2 14
170 14.2 13
180 14.2 13
190 14.2 12
200 14.2 12
210 14.2 12
220 14.2 12
230 14.2 11
240 14.2 11

2nd Charger
Min Volts Amps
0 13.2 36
10 13.2 35
20 13.3 34
30 13.2 12

As explained in my previous posts if the two chargers are connected they both trip into float after about 30 mins so I'm guessing the fault in the 2nd trips the 1st charger into float also.

I'm hoping now I can take this data with me to a service centre and the fault should be clear (last time they were tested we were told they were both fine). Perhaps it is as simple as a component failure with the charger???

[colemj]

Those data seem to suggest that the chargers are set up for gel batteries and not flooded. Absorption voltage seems to be set at 14.2V. This should be 14.8V for Trojan flooded batteries. Your chargers are folding back the current way too soon and not reaching proper voltage.

Mark

[mitiempo]

Originally Posted by Hugh Walker

Well I finally got around to doing some proper testing of the chargers and I've found an obvious fault with the second charger. As was suggested I observed each charger individually connected to only the service bank and took the below measurements. I can see the the 1st charger works pretty much perfectly and was still holding 14.2V after 240 minutes. The second charger starts the same way but after 30 mins it trips into float where it drops down to 13.2V (I discontinued measurements at this time).

1st Charger
Min Volts Amps
0 13.2 36
10 13.2 35
20 13.3 34
30 13.2 32
40 13.2 32
50 13.4 31
60 13.6 31
70 13.6 30
80 13.8 30
90 13.9 28
100 14.0 26
110 14.0 22
120 14.1 18
130 14.2 17
140 14.2 15
150 14.2 14
160 14.2 14
170 14.2 13
180 14.2 13
190 14.2 12
200 14.2 12
210 14.2 12
220 14.2 12
230 14.2 11
240 14.2 11

2nd Charger
Min Volts Amps
0 13.2 36
10 13.2 35
20 13.3 34
30 13.2 12

As explained in my previous posts if the two chargers are connected they both trip into float after about 30 mins so I'm guessing the fault in the 2nd trips the 1st charger into float also.

I'm hoping now I can take this data with me to a service centre and the fault should be clear (last time they were tested we were told they were both fine). Perhaps it is as simple as a component failure with the charger???

When you tested the second charger what was the state of charge before turning the charger on?

[rebel heart]

Originally Posted by colemj

Those data seem to suggest that the chargers are set up for gel batteries and not flooded. Absorption voltage seems to be set at 14.2V. This should be 14.8V for Trojan flooded batteries. Your chargers are folding back the current way too soon and not reaching proper voltage.

Mark

My AC-DC charger (set for flooded) never goes over 14 volts, and the blue sky solar controller (set for flooded) never goes over 14.2 volts. The "low 14's" seems to be pretty standard.

[Hugh Walker]

The chargers (two x dolphin 40A) are definitely both set for wet lead acid, it says in the manual that wet lead acid is 14.4V (although I never see above 14.2) the wet lead acid float voltage according to the manual is 13.2 though which I do see (I can tell float also by the LED lights on the charger itself).

When I took these measurements on consecutive days the battery bank was at around 60% before turning on the chargers. I took care to see they were both fairly similar values before starting.

[colemj]

Originally Posted by rebel heart

My AC-DC charger (set for flooded) never goes over 14 volts, and the blue sky solar controller (set for flooded) never goes over 14.2 volts. The "low 14's" seems to be pretty standard.

Those are low charging voltages. Do they stay that low all the way to float?

Our Victron charger, Iota charger, Morningstar solar controller and both alternator regulators have 14.8V as their flooded settings. As did our previous Outback charger and Trace solar controller. And the Xantrex charger before those.

Trojan's specific charger setting recommendation for their flooded batteries is 14.8V during bulk/absorption.

Your chargers and controller may be sensing their internal outputs and not accommodating for voltage drop to the batteries. If so, you should either add an external voltage sensor (if available) or adjust their outputs so that absorption voltage is proper at the batteries (if possible).

Mark

[colemj]

Originally Posted by Hugh Walker

The chargers (two x dolphin 40A) are definitely both set for wet lead acid, it says in the manual that wet lead acid is 14.4V (although I never see above 14.2) the wet lead acid float voltage according to the manual is 13.2 though which I do see (I can tell float also by the LED lights on the charger itself).

When I took these measurements on consecutive days the battery bank was at around 60% before turning on the chargers. I took care to see they were both fairly similar values before starting.

OK. If it has a setting of 14.4V, then perhaps it is sensing 14.4V and you are measuring 14.2V because you are measuring at the batteries and the charger is probably sensing its internal output. This is common, and the reason it is important to either get a charger with a remote voltage sensor or one with an adjustable output.

So, if that is the case, then you are correct - charger #1 seems to be working correctly, but #2 is not.

Mark