What voltage should my new 'smart charger' maintain the batteries at?

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cygnusv

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A week ago I installed x4 new Trojan T105 225AH 6 volt batteries in series to give me a 24 volt leisure bank. I also fitted a new Victron blue energy 24 volt 12 amp 4 stage charger (The IP67 one with start interrupt feature). The charger is fitted to the 'common' connection of our 1-2-both-off distribution switch. The cables from the switch to each battery bank is heavy duty and the connections are good.

We use the boat every day and the batteries get regularly, but not too heavily exercised - water pumps and lights etc. At present (and for the rest of the winter) we are connected to shore power.

When I first powered up the new kit, the charger went straight into bulk charge, and exercised itself for about 8 hours before going into 'storage mode' via 'float mode'. Over the last few days the battery voltage has remained at 26.4 volts, as per the spec sheet for storage mode.

Does 26.4 volts seem normal? I must admit that I thought the 'maintained' voltage would be higher. :confused:

Edited to add - My main reason for asking this is because we are prone to winter power cuts and will need to run the inverter from time to time.
 
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cygnusv said:
When I first powered up the new kit, the charger went straight into bulk charge, and exercised itself for about 8 hours before going into 'storage mode' via 'float mode'. Over the last few days the battery voltage has remained at 26.4 volts, as per the spec sheet for storage mode.

Does 26.4 volts seem normal? I must admit that I thought the 'maintained' voltage would be higher.
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26.4v is the specified storage mode voltage. However, the charger's data sheet says "The storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours.". Does this apply in your case?
 
I have the same batteries but in pairs making 12v banks, and a sterling charger.

My lot sits at 13.6v with the charger in float, but after an hour disconnected, they sit at 12.8v. So if you double that, you'd get 27.2v and 25.6v.

so sounds about right to me (and my batteries are quite old now too).
 
pvb said:
26.4v is the specified storage mode voltage. However, the charger's data sheet says "The storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours.". Does this apply in your case?
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N0. The batteries are used lots of times a day, every day. This is why I'm wondering if I've got something wrong.
 
cygnusv said:
N0. The batteries are used lots of times a day, every day. This is why I'm wondering if I've got something wrong.
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I wonder what the charger considers to be "subjected to discharge"? Maybe you need to phone Victron and ask whether yours is working correctly or not.
 
pvb said:
I wonder what the charger considers to be "subjected to discharge"? Maybe you need to phone Victron and ask whether yours is working correctly or not.
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Thanks pvb, you make a good point and I think I'll do that. I'm resisting the temptation to turn the charger off then back on again. I did this the other day and the charger went straight into bulk, then float and within half an hour or so, back into storage with the yellow light off.
 
cygnusv said:
N0. The batteries are used lots of times a day, every day. This is why I'm wondering if I've got something wrong.
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But if you are con nected to shore power 24/7 at present then all power usage could be supplied by the charger directly, effectively not discharging you batteries. In that case the voltage would be correct. Probably best to query the manufacturer directly...
 
aluijten said:
But if you are con nected to shore power 24/7 at present then all power usage could be supplied by the charger directly, effectively not discharging you batteries. In that case the voltage would be correct. Probably best to query the manufacturer directly...
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That is very possible, I'm just surprised that the mode light (the yellow one) is out and voltage is only 26.4.

I succumbed to temptation earlier and switched the charger off for 10 minutes. When I turned the power back on, the charger went into bulk mode for a little while then into float. After a total of 4 hours the yellow light went out. This even though water pumps were being used regularly. Confusing....
 
Not trying to hi-jack this thread but if I may I would like to ask a charger related question of the wise heads gathered together here. I have two 220 amp batteries connected together giving 12volts. I have a c-tek 300 charger that tops them up when I'm on shore power. But now I will be leaving the boat in Belgium for nearly three months and I wonder if it is a good idea to leave it connected or should I get a trickle charger or even some other solution? Thanks and sorry for jumping I to your thread.
 
cygnusv said:
That is very possible, I'm just surprised that the mode light (the yellow one) is out and voltage is only 26.4.

I succumbed to temptation earlier and switched the charger off for 10 minutes. When I turned the power back on, the charger went into bulk mode for a little while then into float. After a total of 4 hours the yellow light went out. This even though water pumps were being used regularly. Confusing....
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What aluijten says sounds correct and your charger could meeting the small loads from pumps an lights. If you have been on mains charge for a long time and the batteries are fully charged then 26.4 is in line with Trojan's suggested float voltage.

I'd suggest that you check the temp. corrected SG of the batteries to confirm that they are fully charged (Trojan state 1.277 @ 80F). Re-check them a few days later to confirm that SG readings are stable. If they are fully charged, then 26.4 volts is what you need for long term charging. However, leaving them on charge for a week or two at 26.4V pretty much confirms they are fully charged anyway :D

EDIT: Just looked at spec. for this charger and it says 28.8V and doesn't say it's adjustable. So doesn't seem to be able to reach the 29.6V Trojan recommend.

Another suggestion would be to partly discharge your batteries overnight & check SG to get an idea of charge state. Then put them back on charge and watch the voltage, it should get up to around 29.6V before eventually returning to the float voltage. Only problem might be the time taken to reach 29.6V with a 12A charger if you aren't on the boat for a fair length of time. However, it would confirm that your charger is setup correctly for T105s.

Your charger sounds undersized for 4xT105s if it is only 12A as stated as that's only 5.3% of battery Ah capacity. Trojan suggest a charging at 10-13% of C20 capacity and that would be more like 25-30A and a 40A charger would allow for other loads whilst charging. However, that might not be an issue if you are mostly on shore power and so extended recharge times don't cause you any problems.
 
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I also use the CTEK M300 charger, it is designed so that it can be left on for several months. But will there be any loads at all? If not, I would leave the shore power disconnected. Just self discharge during three months will not harm the batteries.
 
Mistroma said:
What aluijten says sounds correct and your charger could meeting the small loads from pumps an lights. If you have been on mains charge for a long time and the batteries are fully charged then 26.4 is in line with Trojan's suggested float voltage.

I'd suggest that you check the temp. corrected SG of the batteries to confirm that they are fully charged (Trojan state 1.277 @ 80F). Re-check them a few days later to confirm that SG readings are stable. If they are fully charged, then 26.4 volts is what you need for long term charging. However, leaving them on charge for a week or two at 26.4V pretty much confirms they are fully charged anyway :D

EDIT: Just looked at spec. for this charger and it says 28.8V and doesn't say it's adjustable. So doesn't seem to be able to reach the 29.6V Trojan recommend.

Another suggestion would be to partly discharge your batteries overnight & check SG to get an idea of charge state. Then put them back on charge and watch the voltage, it should get up to around 29.6V before eventually returning to the float voltage. Only problem might be the time taken to reach 29.6V with a 12A charger if you aren't on the boat for a fair length of time. However, it would confirm that your charger is setup correctly for T105s.

Your charger sounds undersized for 4xT105s if it is only 12A as stated as that's only 5.3% of battery Ah capacity. Trojan suggest a charging at 10-13% of C20 capacity and that would be more like 25-30A and a 40A charger would allow for other loads whilst charging. However, that might not be an issue if you are mostly on shore power and so extended recharge times don't cause you any problems.
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Hi Mistroma

Thank you for your thoughts. In normal everyday day use the batteries are only asked to support a single Johnson 5.5 amp water pump along with a small amount of low wattage lighting occasionally. Everything else is generally (at this time of year) connected to shore power. When we do take the boat out we have a 24 volt 65 amp alternator to do the honours.

I figured that given our usual type of use, 12 amps ought to be enough to keep the batteries happy.
 
BabaYaga said:
I also use the CTEK M300 charger, it is designed so that it can be left on for several months. But will there be any loads at all? If not, I would leave the shore power disconnected. Just self discharge during three months will not harm the batteries.
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Trojan T105s have a pretty high self-discharge rate and state of charge could drop considerably over 3 months. Trojan's T-105 Datasheet says self-discharge is "Up to 4% per week" (I assume that's probably at a fairly high temp. (>25°C?) and would be less at lower temperatures).

So T-105's could lose "up to" 50% of charge over a 3 month period in warm weather. I couldn't find any data for storage at 0 - 10°C range probably relevant to OP.
 
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