Battery Charging questions

[Lesd]

I've just changed my main domestic bank to Trojan T105 deep cycle batteries and am keen to get the best from them.

 

The domestic bank is paralleled to the start battery and bow thruster battery via a smartbank twin relay system. My question relates to the charge voltages I should be using and the affects these have. I charge in three ways;

 

1. Solar panels

2. Honda Genny (winter mainly)

3. Twin alternators when cruising

 

The charge voltages are 13.8 from the panels (not sure thats correct actually as I type that), 14.8V from Genny/Victron charger, and 14.4V from alternators.

 

The new Trojan batteries say they should be charged at 14.8v with occasional 15.5V equilisation charge.

 

Questions

1. Will I damage the batteries but charging at the lower voltages from the panels and alternators ?

2. If I initiate a equilisation charge at 15.5v will I damage the standard start/BT batteries at 15.5V ?

3. I need to swap the start/BT batteries soon as they are dying, would a calcium based lead acid battery be better for the voltages mentioned above ?

4. Im thinking of swapping the current PWM solar charger for a MPPT unit, do they charge at better voltage levels (14.8v bulk ?)

 

Any other advice ?

 

Thanks

Les

[GUMPY]

You can use the SG/SB to seperate the batteries when the voltage is high

see here

http://smartgauge.co.uk/diff_batts.html

thats how I used to run some AGM batts that didnt like above 14v alongside some normal lead acid.

 

cables are in my boot, awaiting some more lugs, should be here today then just got to put the ends on, should be done in the next couple of days

[Gibbo]

You can use the SG/SB to seperate the batteries when the voltage is high

see here

http://smartgauge.co.uk/diff_batts.html

thats how I used to run some AGM batts that didnt like above 14v alongside some normal lead acid.

 

Agreed. I'd be inclined to go that route, then perform the occasional full equalisation.

[Lesd]

Thanks for the info, I'll look into setting up the smartbank to do that. I guess that answers question 2 from my first post, but does anyone have any views on the other questions?

 

PS Julian, will pm you re the cables, thanks.

[smileypete]

4. Im thinking of swapping the current PWM solar charger for a MPPT unit, do they charge at better voltage levels (14.8v bulk ?)

Roughly depends on how many watts of solar, probably not worth it for a small 'caravan' panel but worth it for the big 'house roof' panels.

 

What controller do you have at the moment? Maybe it drops to 13.8V float voltage after charging for a time at a higher voltage.

 

For small 'caravan' panels there's PWM controllers with variable voltage settings around (this one does two batts/banks)

 

http://www.ebay.co.uk/itm/12-24V-10A-Dual-Duo-two-Battery-Solar-Controller-RVs-UK-/260846095659?pt=UK_Sound_Vision_Battery_Chargers&hash=item3cbba38d2b

 

cheers, Pete.

~smpt~

[Lesd]

Hi Pete

I currently have 2 x 130w Kyocera panels, the controller is a stecca 3030 PWM unit.

Im considering adding a third higher voltage 250w panel with a seperate MPPT controller and considering swapping that Stecca unit over to MPPT at the same time (a seperate unit as the voltages are so different). I'll dig out the manual and compare it to the unit you linked too, you may be right about the float voltage as the batts have been quite well charged when I took that reading the other day.

Les

[Justme]

a seperate unit as the voltages are so different.

 

 

 

What are the peak currents (amps) like for each panel? If they are close you can wire them in series as long as the total voltage is under the controllers max.

 

So you could have

 

 

1 x 200 watt 36v 5.5a panel wired in series with a 130 watt 24v 5.5a panel as long as the controller can take 60v (plus the low temperature voltage increase allowance).

[smileypete]

If your 2x130W Kyrocera's are these:

 

http://www.altestore.com/store/Solar-Panels/100-to-149-Watts-Solar-Panels/Kyocera-KC130-TM-130W-12V-Solar-Panel-w-J-Box/p2403/

 

then there's 100W panels on Ebay that go for as little as £60 which will go nicely in parallel:

 

http://www.ebay.co.uk/sch/m.html?_nkw=100w+solarpanel&_sacat=0&_odkw=&_osacat=0&_armrs=1&_ssn=%28easy%29bay

 

Since the Steca is a 30A controller it should take a couple of extra 100W panels no problem.

 

That'll give you 460W of rated solar panel, at some time you could replace the Steca with a 45A MPPT to give 20%-35% more power into your batts if you need it.

 

Edit: There's also 130W panels from the same seller but might be pushing the limit of the controller.

 

cheers, Pete.

~smpt~

Edited October 4, 2012 by smileypete

[blackrose]

How will you charge at 15.5v Les? Does your Victron charger have some different voltage output settings?

[nb Innisfree]

How will you charge at 15.5v Les? Does your Victron charger have some different voltage output settings?

 

IIRCC our 24v Victron Multiplus can be setup for anything up to 32v so 16v for 12v Victron.

[smileypete]

How will you charge at 15.5v Les? Does your Victron charger have some different voltage output settings?

Looks like Les is living aboard without a shoreline, or aiming to.

 

In that case maybe one or more of his solar panels could be connected direct to the batts, to give enough unregulated charge current to reach the right EQ voltage (when it's sunny of course! ) Might need some sort of resistor or lamp filament to limit current.

 

cheers, Pete.

~smpt~

[blackrose]

Looks like Les is living aboard without a shoreline

 

Yes, he does.

[Lesd]

These are the panels we have at the moment

 

http://www.wholesalesolar.com/pdf.folder/module%20pdf%20folder/KC130GT.pdf

 

output 130w

open circuit Voltage 21.9v

short circuit current 8.02a

max output voltage 17.6v

max output current 7.39a

max system voltage 750v

 

 

Space wise I could easily fit one more large panel of two more of similar dimensions as these so either option is ok space wise. I quite like the idea of a single larger MPPT controller (The Tracer unit Matty recommends looks good), both Pete's and Justme's suggestion only require one controller right ? Is there a preferred option out of these two or is it just a question of cost ?

 

Mike, I'm pretty sure my Victron 12/3000/120 combi can be put into equilisation mode by using the remote panel, I need to dig out my actual manual but I had found one on the net that said it was possible (just need to check its the same on my 5 year old model).

 

Yes, we live aboard with no shore line, I'd just like to increase the solar array in general and make sure its charging at the right voltage for the new batteries (14.8) and to use that Victron charger's capability to give the new trojan batts the best treatment possible.

 

Les

[smileypete]

Space wise I could easily fit one more large panel of two more of similar dimensions as these so either option is ok space wise. I quite like the idea of a single larger MPPT controller (The Tracer unit Matty recommends looks good), both Pete's and Justme's suggestion only require one controller right ? Is there a preferred option out of these two or is it just a question of cost ?

I think a couple of the Ebay 'caravan' type panels will play much better with the existing, than one of the 'house roof' panels.

 

If the two existing and two added panels have the same Vmp of 18V, they could be put in parallel (or series parallel, maybe more on that later...)

 

cheers, Pete.

~smpt~

Edited October 4, 2012 by smileypete

[Lesd]

I think a couple of the Ebay 'caravan' type panels will play much better with the existing, than one of the 'house roof' panels.

 

If the two existing and two added panels have the same Vmp of 18V, they could be put in parallel (or series parallel, maybe more on that later...)

 

cheers, Pete.

~smpt~

 

Thanks Pete, I'll have a look around ebay etc to see whats available. I'd like to use the Tracer MPPT controller so will need to check into that too to see if adding 2 x 100w is the limit or could I push it to 2 x 130w etc. I also get a little confused with the parallel and series/parallel thing !

 

Les

[smileypete]

Thanks Pete, I'll have a look around ebay etc to see whats available. I'd like to use the Tracer MPPT controller so will need to check into that too to see if adding 2 x 100w is the limit or could I push it to 2 x 130w etc. I also get a little confused with the parallel and series/parallel thing !

No problem, best way to explain is with a couple of examples:

 

 

When putting solar panels in series, the current output Imp needs to be the same, and the best way to ensure that is use identical panels.

 

When putting solar panels in parallel, the voltage output Vmp needs to be the same. One way to do that is count the number of solar cells on the panel itself, (each cell has a Vmp of 0.5V)

 

Note Vmp is the voltage output at maximum power, and Imp is the current output at maximum power (not the 'imp' that is a small mythological being or small vintage british car )

 

Clear as mud?

 

cheers, Pete.

~smpt~

Edited October 6, 2012 by smileypete

[Lesd]

Hi Pete

Thanks for posting the pics, thats does make sense. I need to do some more research but so far I can find any 240/250w panels that are 36v, most of the better value units seem to be 30V. With a 45A tracer controller I could go for 2 more 120/130w 18v units which do seem like good value (£60-100 each) or a larger 240/250w unit operating at 36V if I can find one at a decent price.

Les