Not charging - Kubota B7000

[GreensvilleJay]

OK, this is finally making sense

The dynamo has 2 coils in it, sharing a 'common' connection, the Brown wire
Brn goes to one AC terminal of the rectifer
Yel goes to the other AC terminal
This means battery will get a low current charge whenever the engine is running.

When the light switch is turned on, it connects the White wire to the rectifier. This allows for more current, to run lights as well as recharge battery.
So that mystery is solved....

Now the 'rectiifer'.
If it is just a 'full wave bridge', then a DMM with 'diode test' capability will prove that as a bridge is just 4 diodes.
If it actually is a 'regulator' then the diode testing will fail.
I suspect it is just a bridge rectifier. back then simple, cheap, and worked. The ones for sale online are $20 item, so can't be complicated( more parts inside ).
You can buy a bridge rectifier(1000v, 50a) for $2 ,
My hunch is online 'marketing' calls them 'regulator' so everyone knows what it's used for .In the wiring diagram , it's called 'rectifier.

 

[Nuno Barros]

I will go thru diode testing ASAP to confirm that, thanks.

But then you mean, all is working fine then? Is it normal that Rectifier will give around 25v DC then? Or with a NEW and FINE Rectifier I should get a more stable DC voltage and around max 14,5?
And if I buy one of those online rectifiers will not regulate the 12+ DC voltage, you mean? Sorry the questions, is to really confirm your sentences.

So what could be my future?
If as you say this is not a regulator, just a rectifier, how are these tractors working with batteries since 50 years ago?
Or would I need to add a voltage regulator into the output of Rectifier?

 

[GreensvilleJay]

If the rectifier is OK, then yes 25V DC is possible.
Say the dynamo puts out 10 V AC, a full wave bridge rectifier will convert to about 14 volts DC BUT it's not a 'steady state' DC voltage. It's a series of pulses( +ve sine waves) that go from 0 volts to 14 in my example. The battery gets whatever energy is available, between current battery voltage(say 11.5) and the 'peak' voltage(say 14). Google bridge rectifier waveform for some pretty drawings and you'll see what I mean. Also this is a low current charging system, maybe 2-5 amps, so think 'trickle' charger. It could take several hours to totally recharge the battery.
Old skool 3 brush generators on farm tractors and dozers kinda worked the same way...slow charge all day long. Very reliable.

Yes you could add a 'regulator' to the system,something like the 'rectifier/regulator' on B&S engines. It'd actually replace the original 'rectifier'. Probably not worth the effort unless you're rewiring the tractor. Then it does make sense to upgrade.

 

[Nuno Barros]

Never understood well AC and around it
What I'm afraid even with low current (amps) is to deliver 25volts to battery. Wouldn't that kill it?

 

[Nuno Barros]

Check this post.
Some friend who had issues with low voltage, changed the rectifier and outputs good values and seems constant.
Thanks mate

Dynamo - B7001 - low voltage - what to do?

Thanks Dave, https://www.ebay.co.uk/itm/12V-Voltage-Regulator-For-Kubota-Tractor-B7100D-B7100HST-D-B7100HSTE-/181882287967 This is the unit I've got, three wires and a ground, I'd appreciate any help you can offer, will test the machine tomorrow. See the marked up photo of the rectifier...

www.orangetractortalks.com

 

[GreensvilleJay]

No, it's not a constant 25 volts, rather a series of pulses without a lot of energy.
Think of a mountain range,lots of pointy mountain in a row with just a little snow on their peaks.
Totally, there's not a lot of snow so when it melts, no bad floods.

 

[Nuno Barros]

Please check what I've shared. Mate gets 13,5 volts DC after replacing the Rectifier-Regulator. Couldn't be the actual ones makes regulation of voltage?

 

[GreensvilleJay]

The original 'rectifier' only converts AC from dynamo in pulses of DC power
The 'regulator' unit converts AND regulates voltage to 13.5 volts.

The 'regulator' is an upgrade and will improve the charging system. Not by 'leaps and bounds'. Compare the cost of a 'rectifier' module vs the 'regulator' module. It may or may not be worthwhile. The original system probably worked for 4-5 decades,but if you're rewiring the tractor, you might as well install the 'upgrade'.

 

[Nuno Barros]

I'm getting confused sorry.
Understood from you that the online rectifiers saying also regulators are not regulating at all, isn't it?
If you tell me, those also regulate and are not only a bridge diode rectifier, i would be happy to buy it for 20€ and move ahead keeping it to work and battery fine.
Which regulator unit to upgrade are you talking about?
Only options I see in the internet are almost al the same, similar to what I've shown above, e.g. amazon.
Thanks

 

[Nuno Barros]

"The ones for sale online are $20 item, so can't be complicated( more parts inside )."
You mean the ones for sale online have more parts inside and regulates voltage? I firstly understood you say they don't regulate, just rectifier.

 

[GreensvilleJay]

'rectifiers' convert AC voltage into DC voltage BUT do not regulate the voltage

'regulators' control the DC voltage

However the 'regulators' in those ads do BOTH, rectify(change AC into DC ) AND control the voltage.
They should be referred to as 'rectifier-regulators', as they do TWO functions.

I tried to find the B&S patent on the their 'voltage regulator' as it shows whats inside and how it works.Sadly Google can't find it but I have a copy 'somewhere' on this PC or one of the others. I used the patent information to redesign their unit years ago.......

this..

EP0452037B1 - An alternator assembly for an internal combustion engine - Google Patents

..isn't the one I was looking for. it's 20 years newer but similar.

OK, found it ! US patent, 1973.......

 

[Nuno Barros]

The ones I found in amazon and aliexpress says its rectifier and regulator of 12v, so that should be the best option, do you agree?
Then I also need to re-do wiring from positive output from rectifier to main switch and all should be ok to deliver 13.5 volts constant to Battery, I hope.
Thanks

example:

https://www.amazon.es/aqxreight-Estabilizador-Rectificador-Regulador-66611-55250/dp/B0C6NJ3FR5/ref=sr_1_3?__mk_es_ES=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=2CA83H1X125MB&keywords=66611%E2%80%9155250&qid=1704796474&sprefix=66611+55250%2Caps%2C90&sr=8-3

 

[GreensvilleJay]

yes, 'rectifier-regulator' is the best choice.
be sure to take notes and pictures when you rewire !
also try to use same colour of wires as the original wiring , if possible.