Moving from 12v to 6v batteries?

[Tim Good]

The general consensus for long term livaboards is 6v Trojan T-105 batteries are ideal. I'm considering swapping my 4 x sealed 12v batteries for 8 x Trojan 6v batteries.

1. I'll need to wire them up correctly. 4 sets of 2 batteries in series and then paralleled to form a single 12v bank. Is there any general advice for this? Cable length or other considerations?

2. Maintenance wise, does anyone else have Trojan 6v and how often do then need checking or topping off?

3. The easy job would be to just replace my 12v like for like. Do you think it's worth the effort to move to the 6v batteries?

 

[NormanS]

1. Smartguage has lots of useful info.
2. No idea.
3. Probably not.

 

[GHA]

The general consensus for long term livaboards is 6v Trojan T-105 batteries are ideal. I'm considering swapping my 4 x sealed 12v batteries for 8 x Trojan 6v batteries.

1. I'll need to wire them up correctly. 4 sets of 2 batteries in series and then paralleled to form a single 12v bank. Is there any general advice for this? Cable length or other considerations?

2. Maintenance wise, does anyone else have Trojan 6v and how often do then need checking or topping off?

3. The easy job would be to just replace my 12v like for like. Do you think it's worth the effort to move to the 6v batteries?

T105's are great!! Doubt if I'll ever get anything else as a full time liveaboard. I check the water once a month and charge them high (14.8v recommended) from solar with no float to try to get back to 100% every day. (Probably manage it half the time if not more). They drink a bit but not too bad.

They hold the voltage better than anything else I've had. Well worth the effort IMHO.

 

[RobbieW]

Given the T105s usually have a higher ampacity (is that a word?) than SLAs do you really need to do an 8 for 4 swap ? I'd compare the capacity of your current bank and install T105s to either match or increase that capacity. Bear in mind T105s are usually a bit taller than most SLAs so you may also need to rework the battery box.

 

[Mistroma]

I could forward details of T105 water usage over time but it hasn't really changed since 2012. I check every 6 weeks and am pretty certain each cell takes 40-50mls. However, al lot depends on how you use them. I fill to absolute max. given in T105 documentation and use a dry dip to measure the level (Just a little tool I made up).

Your profile has no detail at all, so no idea about details of your boat but it must be quite big if you are considering 7xT105s. I have 4 and that's worked out well. You can check my profile if you want to compare your setup with mine.

I have just checked and put in the following total volumes over 6 summer seasons:
Batt.1: 3.91 ltrs
Batt.2: 3.75 ltrs
Batt.3: 3.620 ltrs
Batt.4: 3.76 ltrs
Total: 15ltrs

This is around 100 mls. per battery per month.

 

[GrahamM376]

Are you using solar? 8 Trojans will take a lot of charging (@ 14.82v) and repeated undercharging kills batteries. My 4 x T125 (same footprint as T105s but higher capacity) take a small amount of water every couple of months.
After various good reports on the Forum, biggest improvement I made last week was to replace Wellsee WS-MPPT30 controller with MPPT Victron Smartsolar, already noticeable improvement in charge rate as can be programmed to suit battery charging regime unlike most which just work to their set program.

 

[Mistroma]

Given the T105s usually have a higher ampacity (is that a word?) than SLAs do you really need to do an 8 for 4 swap ? I'd compare the capacity of your current bank and install T105s to either match or increase that capacity. Bear in mind T105s are usually a bit taller than most SLAs so you may also need to rework the battery box.

I rebuilt my battery box based on published T105 data. Spec. said they wouldn't fit on length/width but when batteries arrived they would actually have fitted the existing box. Height was barely acceptable so I could just get away with using the original box. I decided it was just too much of a squeeze, moved one side by 25mm and dropped the base by 50mm. One advantage was that I could then fit forced ventilation to the top and install a lid. I'd noticed that the previous batteries were causing discolouration to the bunk base. It was well worth the hassle.

 

[Tim Good]

Are you using solar? 8 Trojans will take a lot of charging (@ 14.82v) and repeated undercharging kills batteries. My 4 x T125 (same footprint as T105s but higher capacity) take a small amount of water every couple of months.
After various good reports on the Forum, biggest improvement I made last week was to replace Wellsee WS-MPPT30 controller with MPPT Victron Smartsolar, already noticeable improvement in charge rate as can be programmed to suit battery charging regime unlike most which just work to their set program.

It's a 43ft boat with 360w of solar via a Victron Mppt. When sunny we make plenty of power often topping batteries up to float by midday. Shouldn't be a problem getting them full as we head south.

 

[Tim Good]

previous batteries were causing discolouration to the bunk base. It was well worth the hassle.

Interesting. I have not sailed in warm climes yet so probably a good idea to force ventilate with time PC fans perhaps. Do you leave the forced ventilation on all the time or timed?

Here is a photo of my friends setup? Do you think they should be spaced more for ventilation purposes?

 

[GHA]

It's a 43ft boat with 360w of solar via a Victron Mppt. When sunny we make plenty of power often topping batteries up to float by midday. Shouldn't be a problem getting them full as we head south.

Side note - from obsessive monitoring , might be worth considering ditching the float cycle to actually get the batts back to 100% every day, takes ages even at bulk voltage!

 

[Tim Good]

Side note - from obsessive monitoring , might be worth considering ditching the float cycle to actually get the batts back to 100% every day, takes ages even at bulk voltage!

Is it possible to overcharge or are the Trojans quite resiliant to that?

 

[GrahamM376]

It's a 43ft boat with 360w of solar via a Victron Mppt. When sunny we make plenty of power often topping batteries up to float by midday. Shouldn't be a problem getting them full as we head south.

Unfortunately, I only have 172w on the gantry so bare minimum could do with more but, as the Kyoceras (4 x 43w) cost close to €1,000 many years ago, would hurt to bin them:sorrow: Fine in summer but borderline in winter.

 

[prv]

Here is a photo of my friends setup? Do you think they should be spaced more for ventilation purposes?

Mistroma was talking about gases vented from the top, discolouring the boards above. For that issue, it doesn't matter how closely they're packed next to each other, just that there is airflow across the top of the bank.

I didn't fit fans to mine, but I did add a couple of louvred vents at each end of the locker to let air blow through.

Pete

 

[RobbieW]

Side note - from obsessive monitoring , might be worth considering ditching the float cycle to actually get the batts back to 100% every day, takes ages even at bulk voltage!

Ideally, shouldnt the charger be doing some sort of algorithmic determination of state of charge ? All my charging systems, except wind which is rarely used and doesnt go through a smart controller anyway, only switch to float when a voltage / current criterion is satisfied ie at 14.6v and current less than 7a (1% of capacity) for 15 mins or something like that. There are times, motoring for extended periods, when I'd baulk at putting 14.6v into the bank for 48hrs.

 

[RobbieW]

...
1. I'll need to wire them up correctly. 4 sets of 2 batteries in series and then paralleled to form a single 12v bank. Is there any general advice for this? Cable length or other considerations?
...

I have a similar configuration using 6v GC2 size batteries, not T105s though. I have them in series pairs to a common bus which is where the interconnect to boat systems is done. This worked in the physical space I had and allowed me to roughly equalise the cable lengths used.

 

[GHA]

Is it possible to overcharge or are the Trojans quite resiliant to that?

Not sure there's any definitive data, but an hour or so at full charge /bulk voltage I reckon is *much* less harmful than constantly being partial state of charge. Millions of cars and vans with newer alternators sit at high voltage all day every day.
There's a substantial paper behind a firewall somewhere which recommended 15.3V! Once a week at least anyway, with 2 x 105's & 300W solar, fridge & laptop on a lot I'll make it to full charge most days but only just.

For your perusal....
https://www.homepower.com/view/?file=HP89_pg120_IPP

http://www.battcon.com/PapersFinal2016/Arioli Paper 2016.pdf

http://www.cruisersforum.com/forums...tor-bulk-charge-issue-179406.html#post2389968

 

[Plevier]

GHA is right, undercharge is both more likely and more damaging. However you must watch the water level if you spend much time above about 14.2. you should not use this level for really long periods.
Those two papers GHA links to are excellent, especially the battcon one. Masses of authoritative information.

 

[Tim Good]

Hmmm... so basically if I switch to 6v I need to have reasonable access to my batteries which I don't currently. Might need to do so rejigging to check them every 4 weeks. Just topped up with distilled water right? I,e water left overnight on the counter top?

 

[GHA]

I could forward details of T105 water usage over time but it hasn't really changed since 2012. I check every 6 weeks and am pretty certain each cell takes 40-50mls. However, al lot depends on how you use them. I fill to absolute max. given in T105 documentation and use a dry dip to measure the level (Just a little tool I made up).

Your profile has no detail at all, so no idea about details of your boat but it must be quite big if you are considering 7xT105s. I have 4 and that's worked out well. You can check my profile if you want to compare your setup with mine.

I have just checked and put in the following total volumes over 6 summer seasons:
Batt.1: 3.91 ltrs
Batt.2: 3.75 ltrs
Batt.3: 3.620 ltrs
Batt.4: 3.76 ltrs
Total: 15ltrs

This is around 100 mls. per battery per month.

Your record keeping is exceptional

So go on then, what's a dry drip?

The lollipop stick with some sharpie marks works but it's been in the mental "must be a better way?" list for a while.

 

[vas]

you are aware that there is an autofilling kit for the T105s right?
Only problem one may have is that it needs an extra 10cm or so above the batteries (that's my understanding, haven't seen live this thing)

I have enough space and I'll fit that, but I'm more concerned on temps. My 4X105 (not bought yet, will do at easter time) will be in the e/r, with two big pieces of metal, temps go north of 50C and are slow to respond and lower. Will have to do tests (never bothered!) but I cannot move the batteries elsewhere and it's extremely difficult to isolate them thermally from the flaps.

V.