Battery Tender

[Big D]

I want to build a battery tender for my cars and motor cycles. This device will keep the batteries charged and so prolong their life span.
Can anybody help, please?

 

[crutschow]

It's called a battery charger. Get one that automatically goes into a trickle-charge mode when the battery is charged.

 

[Big D]

But surely it is much more fun to built one!!!

This system does not just go into trickle mode, it monitors the battery current and when it runs down slightly it charges the battery again, thus keeping the battery in operation all the time.

If this is total BS, I apologise, but this is what I was told.

The original units can be found at Batterytender.com - Home of All Your Charging Needs

 

[mneary]

Battery Tender brings to mind an auxiliary (towed) vehicle containing extra batteries.

The "BatteryTender" looks like an assembly of four $25 smart motorcycle battery chargers in one box, for $249. Nice if you're keeping four motorcycles within a six foot circle. Still awfully expensive.

 

[crutschow]

That device sounds like a fancy battery charger that drops into a trickle charge mode when the battery is charged. For example one of their website FAQs states:

How is the Battery Tender Plus battery charger different from a trickle charger?
The Battery Tender Plus battery charger delivers 1.25 amperes during bulk charge mode, holds the battery charge voltage constant at 14.4 VDC during absorption charge mode until the battery charge current drops to 0.1 amperes at which time it then automatically switches to a float charge mode. During float charge mode, the output voltage of the Battery Tender Plus battery charger is 13.2 VDC, which is well below the gassing voltage of a lead acid battery. This keeps the battery topped off, while minimizing any detrimental effects to do gassing. The Battery Tender Plus battery charger is able to perform these complex switching functions because its electronic circuitry is controlled by an on board microprocessor.

I believe most commercial battery chargers that state they automatically go to a trickle charge mode when the battery is charged do a similar thing. Trickle charge typically means keeping the battery at a voltage lower than the normal charge voltage.

To build one you would need to program a microprocessor to do what it does. If you want to to that, go for it, but it's a lot of work and expense to reinvent the wheel. It'll likely cost you several times what a commercial unit costs.

 

[Nigel Goodwin]

As all you're wanting to do is keep the batteries in good condition, you don't need a 'charger' at all - just a simple trickle charger would do fine, and it's dead simple (transformer, bridge, resistor - that's it).

 

[Big D]

Nigel, it might be easy for you, but you are talking to a dumb mechanical guy now. If it is possible, i would need a diagram for this so I can get a hold of the parts.
HELP!!!!!!!!!!!!

 

[3v0]

If it is money you want to save watch harbor freight for a sale. I think I got a trickle charger for about $5 a few years back.

If you really want to keep batteries in good shape you need to do some web serfing and read up on what others are doing.

3v0

Nigel, it might be easy for you, but you are talking to a dumb mechanical guy now. If it is possible, i would need a diagram for this so I can get a hold of the parts.
HELP!!!!!!!!!!!!