Relays better than diodes for split charging?

[JimC]

My boat has the usual diode splitter for distributing the alternator's charge between the engine and service batteries. This has the disadvantage that the forward voltage drop of the diodes is not "seen" by the alternator so the batteries are never charged to the maximum (I've confirmed this by meter checks). I could buy one of the battery sensing regulators such as Adverc or Sterling to overcome this: cost about £150.

My campervan uses a simple voltage sensitive relay to do the same job. All the charge goes to the engine battery until its voltage reaches about 14v, then the relay energises and connects the service battery to the alternator in parallel to the engine battery so they share the charge. On the face of it seems a cheaper and better system with no energy wasted in overcoming the voltage drop in the diodes. Is so why aren't we all using it - or am I missing something?

 

[sailorman]

My boat has the usual diode splitter for distributing the alternator's charge between the engine and service batteries. This has the disadvantage that the forward voltage drop of the diodes is not "seen" by the alternator so the batteries are never charged to the maximum (I've confirmed this by meter checks). I could buy one of the battery sensing regulators such as Adverc or Sterling to overcome this: cost about £150.

My campervan uses a simple voltage sensitive relay to do the same job. All the charge goes to the engine battery until its voltage reaches about 14v, then the relay energises and connects the service battery to the alternator in parallel to the engine battery so they share the charge. On the face of it seems a cheaper and better system with no energy wasted in overcoming the voltage drop in the diodes. Is so why aren't we all using it - or am I missing something?

some of us have for years mine is a victron cyrix http://www.victronenergy.com/battery-isolators-and-combiners/cyrix-80a-160a-400a/

 

[VicS]

You have identified the problem with diode splitters. If it were not for the forward volts drop they would proabably be the ideal solution. To certain extent of course you can over come it by using a battery sensing alternator but given two battery banks you then have to decide which bank to sense. It would not matter if the volts drop across the diodes was fixed but it is not, it varies with current. So the drop is bound to be different across the two diodes of the splitter.

Voltage sensing relays seem to over come the problems with the diode splitter although one battery does have priority over the other and that starts another debate! They seem to be the favoured method at the moment although a visit to the website of someone making diode splitters but not VSRs will tell you all the advantages that diodes have over VSRs

Something along the lines of Sterling's Alternator to Battery chargers is another solution. They offer controlled multistage charging of the house battery and independent basic charging of the starter battery. Some clever electronic wizardry involved with those that might not be to everyone's liking.

 

[alan]

Relays better than Diode for Split Charging

There are a couple of ways of achieveing this: there are a number of SCRs around (BEP marine e.t.c.) and also there are "diode" splitters which use transistors instead of diodes which have effectively no drop (or very little) (e.g. www.dg2k.co.uk/xsplit.htm). Going down the Adverc or Sterling route is not the only solution.

Alan.

 

[alahol2]

The 'middle way' is a normal relay enrgised by the charging or oil warning indicator lamp circuit. A lot cheaper than a VSR, but it does charge both batteries at the same time rather than preferring one.

 

[ghostlymoron]

I had this same conundrum when my diode splitter packed up last year. I went down the VSR route and am very happy with the outcome. I installed a BEP unit which is simple to fit as long as you can get to the terminals, have nimple fingers and can borrow a large crimping tool for fitting the cables to the main switches. The cost of the BEP is about £50 - so not too expensive either.

 

[halcyon]

On the face of it seems a cheaper and better system with no energy wasted in overcoming the voltage drop in the diodes. Is so why aren't we all using it - or am I missing something?

Not sure. thats life.

Follow link, and mouse over the litrature thumbnail on the lower left, explains the system, and that was in Jan 1982. So voltage sensing for split charging has been around for years.

http://www.kddpowercentre.com/page6.html

In the 80's relay charging was common, but into the 90's penny pinching, and accountants became the in thing. Diodes splitters are very cheap, not that good did not count.

All the systems have good points and bad points, relays probably have the most good points.


Brian

 

[sailorman]

Durite do a 2 or 3 way solid state no-loss "relay" as well, but whichever method you choose should depend on your motoring pattern.
~If you choose a relay, the batteries are put in parallel when the volts reach about 13.4 on the starter battery. If the domestic bank had been heavily discharged, and the alternator is not quite big, the relay will drop out again as the good battery is dragged down to the lowest common denominator. This on/off chatter can be "slugged" but the LCD problem remains, and when the relay does eventually stay in, the start battery will not get a good voltage potential diference until the domestic bank has risen to match it.
That may happen quite a long time after the charge sequence starts - ie a longish motoring session - is that your normal way of life?
Diodes keep them separate, and even better a smart charger will sense the bank it's connected to (usually domestic) and 'force feed' it. During the time spent topping up the domestic bank, the other (less discharged) batteries tend to get a longer absorbtion cycle and stay ahead of the domestic bank rather than being dragged down to its level.
Putting batteries in parallel can be a black art. When we used them in computer UPS, they had to be matched, and if we changed one , we changed all.

My Cyrix is rated @ 200A

KIN Clock is 6 min slow

 

[boatmike]

Vic, I think you have succeeded in giving the arguments for and against without bias there. Well done! Too often on here the answers are black and white and one solution is the dogs whatsits and the other is rubbished. Both approaches have their merits. Provided that Diodes are not overloaded they are reliable solid state devices. Relays are electro mechanical and do in fact wear out and give problems over time. They are clearly better in terms of not having a voltage drop but with the right wiring a battery sensed alternator will lift it's output to overcome this. Most alternators are in fact battery sensed anyway so the question of which battery you want to sense on exists I think with either device does it not? I also agree that fitting a smart charger such as a Sterling, which I have on my system overcomes the diode voltage drop problem. There is only one thing I would add though and that is if like me you have a large alternator be careful to make sure the diodes and/or relays are rated for the current. When my service bank is severely depleted the alternator commonly charges at over 30 amps. Many diodes are only rated at 25 and will overheat and blow if higher currents are seen. Relays will just burn out ther contacts.

 

[Billjratt]

Durite do a 2 or 3 way solid state no-loss "relay" as well, but whichever method you choose should depend on your motoring pattern.
~If you choose a relay, the batteries are put in parallel when the volts reach about 13.4 on the starter battery. If the domestic bank had been heavily discharged, and the alternator is not quite big, the relay will drop out again as the good battery is dragged down to the lowest common denominator. This on/off chatter can be "slugged" but the LCD problem remains, and when the relay does eventually stay in, the start battery will not get a good voltage potential diference until the domestic bank has risen to match it.
That may happen quite a long time after the charge sequence starts - ie a longish motoring session - is that your normal way of life?
Diodes keep them separate, and even better a smart charger will sense the bank it's connected to (usually domestic) and 'force feed' it. During the time spent topping up the domestic bank, the other (less discharged) batteries tend to get a longer absorbtion cycle and stay ahead of the domestic bank rather than being dragged down to its level.
Putting batteries in parallel can be a black art. When we used them in computer UPS, they had to be matched, and if we changed one , we changed all.

 

[PetiteFleur]

Just to put the cat amongst the pigeons - have you read the technical info from 'Smartgauge'? See:- http://www.smartgauge.co.uk/controllers.html
Lots more technical info on the site as well.

 

[smeaks]

i use a caravan vsr (chrages the fridge when towing) if the batteries are pulling load the charging cables dont carry load, i just keep on one battary that charges and when the start voltage drop is negated by the alternator the house battary also charges... three years no problem cost about £7 from memory.

 

[cimo]

My boat has the usual diode splitter for distributing the alternator's charge between the engine and service batteries. This has the disadvantage that the forward voltage drop of the diodes is not "seen" by the alternator so the batteries are never charged to the maximum (I've confirmed this by meter checks). I could buy one of the battery sensing regulators such as Adverc or Sterling to overcome this: cost about £150.

My campervan uses a simple voltage sensitive relay to do the same job. All the charge goes to the engine battery until its voltage reaches about 14v, then the relay energises and connects the service battery to the alternator in parallel to the engine battery so they share the charge. On the face of it seems a cheaper and better system with no energy wasted in overcoming the voltage drop in the diodes. Is so why aren't we all using it - or am I missing something?

Its a subject that is getting alot of airplay here recently. If we all had identical onboard power usage patterns I suppose we would all eventually migrate to the same charging arrangement. But given the rich diversity of boats & their use, you can't be surprise at the number of products & conflicting advice available out there.

Your question,Jim, is about battery charging? The method you employ is really about acheiving the best you can afford that will be "nearest" to suitable for your own requirements (a statement of no help whatsoever!).

Folks here will already know I'm a big advocate of simplicity (or just simple perhaps!). I continually sing the praises of charging through a 1-2-both selector switch. I have to smile a bit each time I read manufacturers liturature on VSRs. They usually start off running down the 1-2-both switch in the first paragraph! (could it be that these VSRs are a replacement for the1-2-B switch I wonder?). The fact that alot of (majority of?) installations still use stock Alternators, which are seldom suitable for the demands being placed on them, dosen't seem to enter into it!

Its an interesting subject. You can spend as much of your hard earned as you like on the bits of kit. The more you add, the higher the complexity, which in turn is inversely proportional to overall system reliability - which kind of brings you back to the position you started from.

To anyone considering purchasing a VSR, I would suggest that they invest the money in a decent multimeter & a couple of shunt guages to monitor the current flows. Once your usage pattern is established & understood, informed decisions can be made. Liveaboards like Brian here wouldn't be without his battery monitor I bet.

(thats more than enought from me!)

rgds
cimo

 

[mikeplummer]

Smartguage / Smartbank

As mentioned by M33; feedback on Smartguage.

I fitted a Smartguage Advanced earlier this year, when I extended the battery capacity and decided that it might be useful if the battery charger also charged the engine start battery as well as the domestics. Previously the start battery was only charged via the alternator.

To date I am quite happy with the set up. I have, however, kept the diode system in the electrical spares locker for reconnection in case the Smartguage system fails.

In terms of relay contact failure, I doubt if this is a problem with the relays specified with the Smartguage system.

I recommend visiting the Smartguage website and reading the installation and users instructions to understand the ramifications of a smart relay system.

Mike

 

[mcframe]

Nut splitter == crimp tool

I had this same conundrum when my diode splitter packed up last year. I went down the VSR route and am very happy with the outcome. I installed a BEP unit which is simple to fit as long as you can get to the terminals, have nimple fingers and can borrow a large crimping tool for fitting the cables to the main switches.

FWIW, I /think/ I've successfully crimped my 4AWG cables by:
(1) Drilling a couple of 2mm holes in the connectors
(2) 'Crimping' them with careful application of a nut splitter every 90 degrees
(3) Using a small blowtorch to draw solder through the holes.

I did cheat slightly by getting a couple of pre-made 6" to 18" lugged cables from Merlin, and only had to crimp onto the original battery cables.

 

[mcframe]

I continually sing the praises of charging through a 1-2-both selector switch. I have to smile a bit each time I read manufacturers liturature on VSRs. They usually start off running down the 1-2-both switch in the first paragraph! (could it be that these VSRs are a replacement for the1-2-B switch I wonder?).

How does a 1-2-both switch use solar to keep *both* my engine & house bank topped up when I'm not on the boat?

Do you keep a YTS'er in the bilges with a multimeter?

 

[VicS]

How does a 1-2-both switch use solar to keep *both* my engine & house bank topped up when I'm not on the boat?

Simple. instead of one big solar panel use two smaller ones. One for each battery. A very small one for the starter battery and a not so small one for the big house battery.

Or maybe there's a regulator with two outputs

Or instead of one blocking diode for the panel two separate diodes, one for each battery.

Do you keep a YTS'er in the bilges with a multimeter?

What's a YTS'er (my multimeter is a plastic bag ... when I know what I'm looking for I'll see if there's one in the bag.)

 

[Stu Jackson]

How does a 1-2-both switch use solar to keep *both* my engine & house bank topped up when I'm not on the boat?

The switch has nothing to do with it, it is how the charging source is wired. Moving charging sources of any type OFF the C post of the 1-2-B switch and to the batteries is now the preferred way. That way you leave the sdwitch off when you're not there, and only use the switch for battery bank output choice. There have been a good number of helpful discussions about this recently.

The solar issue can be handled two ways: as suggested with two panels, one to each bank, or one solar panel to a selected bank (UK seems to prefer the engine bank, US seems to prefer the house bank) with a relay that closes when charging voltage meets a specified level and connects the banks and then opens when the sun goes down to separate the banks.

Do a search on "1-2-B switch" and "battery charging" for the recent discussions which go into a great deal of detail. Here's one for example: http://www.ybw.com/forums/showthread.php?t=226726

Solar charging is just like alternator charging: one source to multiple recipients.

 

[cimo]

How does a 1-2-both switch use solar to keep *both* my engine & house bank topped up when I'm not on the boat?

Do you keep a YTS'er in the bilges with a multimeter?

I think Vics has answered the first part.

YST'er (?) - I must brush up on my txt speak!. Sounds expensive, i'm sure I don't have one whatever it is!

 

[alahol2]

"Do you keep a YTS'er in the bilges with a multimeter? "

YTS = Youth Training Scheme ie an underpaid (unpaid?) youngster desperate for a proper job.